BGP route advertisement
I am confused about which routes will a bgp speaker advertise to its bgp neighbors?
Will it advertise the bgp routes in routing table OR will it advertise the best routes from the bgp table (but not necessarily in routing table)?
Thanks!!
I thought so, but in Troubleshooting IP Routing Protocols book by Cisco press, it is stated that bgp router will advertise its routes from routing table, so wanted to confirm that that was indeed wrong.
On page 668, this is what is written:
One rule that BGP follows when advertising prefixes to other neighbors is that the prefix being advertised must
exist in the routing table of the advertising router.
Similar Messages
-
I have two routers that has a static route configured for the LAN side which re-distributes via BGP to the WAN.
One of the routers does not have anything connected to LAN subnet/ interface. Other one is live.
Will this create a routing conflict in the network ?Yes, there is an issue here.
why the secondary router is advertising the LAN routes while it doesn't have reachabiility to the LAN.
In case if you are planning to connect the LAN lter it is recomended to configure the static routes with the exit interface.
i.e Ip route x.x.x.x y.y.y.y [LAN interface] [next hop ip add]
Ahmed -
TOC-BP-SWa#sh ip bgp neighbors 10.14.0.3 advertised-routes
BGP table version is 1674320, local router ID is 10.14.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 10.14.0.1/32 0.0.0.0 0 32768 i
*> 147.249.37.0/24 172.20.18.1 120 0 2001 65015 65016 64823 7381 64681 i
*> 147.249.38.0/24 172.20.18.1 120 0 2001 65015 65016 64823 7381 64681 i
*> 147.249.46.0/24 172.20.18.1 120 0 2001 65015 65016 64823 7381 12159 12159 i
*> 147.249.196.0/24 172.20.18.1 120 0 2001 65015 65016 64823 64870 65124 i
*> 147.249.237.0/24 172.20.18.1 120 0 2001 65015 65016 64823 7381 64681 i
TOC-BP-SWa#sh ip bgp neighbors 10.14.0.3 received-r
Total number of prefixes 0
TOC-BP-SWa#sh ip bgp neighbors 10.14.0.2 received-r
BGP table version is 1674320, local router ID is 10.14.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i10.14.0.2/32 10.14.0.2 0 100 0 i
* i147.249.37.0/24 10.14.0.2 0 120 0 2001 65015 65016 64823 7381 64681 i
* i147.249.38.0/24 10.14.0.2 0 120 0 2001 65015 65016 64823 7381 64681 i
* i147.249.46.0/24 10.14.0.2 0 120 0 2001 65015 65016 64823 7381 12159 12159 i
* i147.249.196.0/24 10.14.0.2 0 120 0 2001 65015 65016 64823 64870 65124 i
* i147.249.237.0/24 10.14.0.2 0 120 0 2001 65015 65016 64823 7381 64681 i
Can this output be duplicated with an OSPF command?Not really because OSPF does not advertise routes it sends LSAs to it's peers.
So you need to look at the OSPF database ie. -
"sh ip ospf database"
which will show you all the LSAs the router is aware of.
In terms of all the LSAs the router has received it will show all of those but it will also show you LSAs that were generated by the router itself although the advertising router IP will point to that being the case.
In terms of all the LSAs the router advertises again it depends on the area and how that has been configured.
So for example an ABR might well have external LSAs (which aren't tied to any area in the OSPF database) but that doesn't necessarily mean it is advertising them to peers within an area as it could have been configured not to.
So it gives you a good idea but you need to also work out a few things for yourself as well.
Jon -
BGP default route advertisement - change preference
hi guys,
I would appreciate some assistance here. We have a primary head office & a DR site. Routers at both sites connect to our carrier for an IP VPN service using BGP. BGP configs on each router advertise a default route 0.0.0.0.
#sh ip bgp neighbors x.x.x.x advertised-routes
BGP table version is 358, local router ID is x.x.x.x
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Originating default network 0.0.0.0
Issue is, some of our remote sites prefer the DR router path for traffic destined to internet.
We are advertising multiple default routes to our carrier, and based on feedback from carrier, route with lowest MED is preferred.
This brings me to what i need to change from my side. Need to change the route preference so that from our remote offices, only the route to head office is preferred with DR site the least preferred route. I know there are multliple ways of doing this, however keen to get input from the experts out there.
DR site router has this BGP config currently applied:
router bgp XXXXX
bgp log-neighbor-changes
redistribute connected
redistribute ospf 1 match internal external 1 external 2
neighbor x.x.x.x remote-as XXXX
neighbor x.x.x.x default-originate
neighbor x.x.x.x soft-reconfiguration inbound
neighbor x.x.x.x route-map IMPORT-POLICY in
neighbor x.x.x.x route-map OPI-route-advertisement out
default-information originate
Removing the "neighbor x.x.x.x default-originate" is not an option, as we need to have the ability to failover to DR at any point.
Thanks in advance & if you need any further info pls advise.
RamaHi Milan,
Thanks. Answers below:
Does it provide an MPLS backbone to you? YES
Are you using the same AS number on all your sites or different ones? Same AS
Any way, what about advertising the default route from your DR site with the site AS number prepended several times (5 times, e.g.)? That's the thing I am struggling to understand as the route-map OPI-route-advertisement already has it prepended 2 times. Shouldn't that be enough to influence which route is least preferred?
route-map OPI-route-advertisement permit 20
match ip address prefix-list xxx default-route
set as-path prepend XXXXX XXXXX
If your provider would permit that and hasn't configured his routers to ignore the AS_PATH length (as him a question), it should make the default route advertised from your DR less preferred within your backbone. Will ask.
Given this, any other thoughts/questions?
Thanks, Rama -
Sh bgp: received & advertised routes
Dear all:
In reference at the commands:
- sh bgp neighbor A.B.C.D
- sh bgp neighbor A.B.C.D received routes
- sh bgp neighbor A.B.C.D advertised-routes
For example:
ROUTER#sh bgp neighbor A.B.C.D
Policy for incoming advertisements is PEERING-IN
Policy for outgoing advertisements is PEERING-OUT
1 accepted prefixes, 0 are bestpaths
Cumulative no. of prefixes denied: 8974070.
No policy: 0, Failed RT match: 0
By ORF policy: 0, By policy: 8974070
Prefix advertised 77, suppressed 0, withdrawn 2
In output this command we have # Prefixes:
1 accepted & 0 are bestpaths (after policy)
advertised 77, suppressed 0, withdrawn 2 (after policy)
8974070 prefix are deny
But, when you execute the next command:
ROUTER#sh bgp neighbor A.B.C.D received routes
Processed 503233 prefixes, 503233 paths
In output this command we have# Prefixes = 503233
And when you execute the next command:
ROUTER#sh bgp neighbor A.B.C.D advertised-routes
Processed 73 prefixes, 73 paths
In output this command we have:
73 prefixes advertised at peer
The question is:
What's the different between counter 8974070 and 503233 (prefix received before apply policy)?
What's the different between counter 77 (or 75 = 77 - 2 withdrawn) and 73 (prefix advertised before apply policy)?
Exist only one command that help at see total prefix received/advertised (different a sh bgp neighbor A.B.C.D received routes) ?
Thanks.Not really because OSPF does not advertise routes it sends LSAs to it's peers.
So you need to look at the OSPF database ie. -
"sh ip ospf database"
which will show you all the LSAs the router is aware of.
In terms of all the LSAs the router has received it will show all of those but it will also show you LSAs that were generated by the router itself although the advertising router IP will point to that being the case.
In terms of all the LSAs the router advertises again it depends on the area and how that has been configured.
So for example an ABR might well have external LSAs (which aren't tied to any area in the OSPF database) but that doesn't necessarily mean it is advertising them to peers within an area as it could have been configured not to.
So it gives you a good idea but you need to also work out a few things for yourself as well.
Jon -
I have two routers with BGP configured:
C2921:
router bgp 65014
bgp router-id 192.168.54.190
bgp log-neighbor-change
neighbor 192.168.54.150 remote-as 65011
neighbor 192.168.54.150 description Loud backup
neighbor 192.168.54.150 route-map Backup out
C1841:
router bgp 65011
no synchronization
bgp router-id 10.10.35.1
bgp log-neighbor-changes
neighbor 192.168.54.149 remote-as 65014
neighbor 192.168.54.149 description Cubus backup
neighbor 192.168.54.149 prefix-list Loudenia out
neighbor 192.168.54.149 route-map Backup out
ip prefix-list Loudenia seq 5 permit 10.10.35.0/24 le 32
ip prefix-list Loudenia seq 10 permit 192.168.111.0/24 le 32
ip prefix-list Loudenia seq 15 permit 10.25.15.0/24 le 32
ip prefix-list Loudenia seq 20 permit 192.168.44.0/24 le 32
ip prefix-list Loudenia seq 25 permit 192.168.45.0/24 le 32
ip prefix-list Loudenia seq 30 permit 192.168.46.0/28 le 32
ip prefix-list Loudenia seq 35 permit 192.168.49.196/30 le 32
ip prefix-list Loudenia seq 40 permit 192.168.49.225/32
ip prefix-list Loudenia seq 45 permit 192.168.49.229/32
route-map Backup permit 10
set as-path prepend 65011 65011
I have added:
ip prefix-list Loudenia seq 50 permit 192.168.48.225/32
made:
clear ip bgp 192.168.54.149 soft
but nothing changed route to 192.168.48.225 not advertised:
C1841-Loudenia#show ip bgp neighbors 192.168.54.149 advertised-routes
BGP table version is 137998, local router ID is 10.10.35.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 10.10.35.0/24 0.0.0.0 0 32768 i
*> 10.25.15.0/24 192.168.111.10 0 32768 i
*> 192.168.44.0 192.168.49.26 0 65005 i
*> 192.168.45.0 192.168.49.26 0 65005 i
*> 192.168.46.0/28 192.168.49.26 0 65005 i
*> 192.168.49.196/30
192.168.49.26 0 65005 i
*> 192.168.49.225/32
192.168.49.26 0 0 65005 i
*> 192.168.49.229/32
192.168.49.26 0 65005 i
*> 192.168.111.0 0.0.0.0 0 32768 i
C1841 knows 192.168.48.225/32 via bgp
* 192.168.48.225/32
192.168.49.58 0 65005 65005 65005 65006 65013 i
*> 192.168.49.26 0 65005 65006 65013 i
I will be grateful for your adviceHello, thanks for reply.
The route is on the route table
C1841-Loudenia#show ip route | i 192.168.48.225
B 192.168.48.225/32 [20/0] via 192.168.49.26, 3w6d
C1841-Loudenia#show ip bgp | i 192.168.48.225
* 192.168.48.225/32
192.168.49.58 0 65005 65005 65005 65006 65013 i
*> 192.168.49.26 0 65005 65006 65013 i -
EIGRP vs BGP route path selection scenario
I am looking for a routing solution to the following scenario. It is a fairly simple design.
I have two WAN connections between sites A and B. One is a 20 Meg Metro Ethernet Circuit running EIGRP. The other is a 10 Meg MPLS running BGP. What do I need to do in my configuration to make sure that the 20 Meg connection is the chosen path based off the fact that it has better speed and bandwidth? It appears to me that the MPLS is the preferred path even though it is slower.
See attached Diagram:
Site A Config
interface GigabitEthernet1/0/12
description PADC COX P2P 20 Meg
no switchport
bandwidth 20480
ip address 172.20.1.1 255.255.255.252
interface GigabitEthernet2/0/2
description LEVEL 3 MPLS
no switchport
bandwidth 10240
ip address 172.22.0.2 255.255.255.252
router eigrp 1
network 10.0.1.0 0.0.0.255
network 172.20.1.0 0.0.0.3
network 192.168.76.8 0.0.0.3
redistribute bgp 65003 metric 100 1 255 1 1500 route-map MPLS_NETWORKS
redistribute static route-map DEFAULT_ROUTE
router bgp 65003
bgp log-neighbor-changes
redistribute static
redistribute eigrp 1
neighbor 172.22.0.1 remote-as 1
default-information originate
Site B Config
interface GigabitEthernet0/1
description COX Communications 10 Meg to Venyu
bandwidth 20480
ip address 172.20.1.2 255.255.255.252
duplex auto
speed auto
service-policy output VOIP
interface GigabitEthernet0/2
description Level 3 MPLS
bandwidth 10240
ip address 172.22.1.2 255.255.255.252
duplex full
speed 100
router eigrp 1
network 10.3.1.0 0.0.0.31
network 10.52.1.0 0.0.0.255
network 10.76.6.0 0.0.0.255
network 172.20.1.0 0.0.0.3
network 192.168.63.64 0.0.0.63
network 192.168.76.249 0.0.0.0
passive-interface default
no passive-interface GigabitEthernet0/0
no passive-interface GigabitEthernet0/1
router bgp 65003
bgp log-neighbor-changes
network 10.3.1.0 mask 255.255.255.224
network 10.52.1.0 mask 255.255.255.0
network 10.76.6.0 mask 255.255.255.0
network 192.168.76.249 mask 255.255.255.255
neighbor 172.22.1.1 remote-as 1If each router is receiving advertisements for the same networks/subnet masks from both BGP and EIGRP it will always choose the BGP routes because they have a lower AD ie. 20 vs EIGRP 90.
Doesn't matter what the bandwidth is.
If you want to prefer the 20Mbps links then there are a number of options -
1) if you can summarise each sites subnets then advertise the summary via BGP and the more specific via EIGRP. More specific will be chosen even before AD is taken into account.
2) change the AD of either BGP or EIGRP so EIGRP ends up with the lower AD
3) run BGP on both links although you would still need to manipulate the attributes to make sure the link you want is used.
Jon -
MPLS BGP routes push to DMVPN spokes
I have an MPLS with BGP. I also have sites that are not connected directly to the MPLS, but have a s2s VPN to hub sites that are connected to the MPLS and that way they access the MPLS resources. I need to communicate the route changes to the MPLS when the DMVPN fails-over to another hub.
Currently this is my config:
Datacenter (MPLS only)
interface GigabitEthernet0/1
description MPLS
ip address 192.168.0.34 255.255.255.252
interface Vlan2
ip address 192.168.96.2 255.255.255.0
router bgp 65511
bgp log-neighbor-changes
network 192.168.96.0
neighbor 192.168.0.33 remote-as 65510
Hub site 1 (MPLS + internet)
interface Tunnel200
ip address 10.99.99.1 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp authentication auth
ip nhrp map multicast dynamic
ip nhrp network-id 12345
ip nhrp holdtime 600
tunnel source GigabitEthernet0/0
tunnel mode gre multipoint
tunnel key 200
tunnel protection ipsec profile dmvpn
interface GigabitEthernet0/1
description MPLS
ip address 192.168.1.2 255.255.255.0 secondary
ip address 192.168.0.2 255.255.255.252
router bgp 65001
bgp log-neighbor-changes
network 192.168.1.0
network 192.168.21.0
!10.99 clients are DMVPN spokes
neighbor 10.99.99.3 remote-as 99010
neighbor 10.99.99.3 route-reflector-client
neighbor 10.99.99.21 remote-as 99001
neighbor 10.99.99.21 route-reflector-client
!as 65000 is the MPLS PE
neighbor 192.168.0.1 remote-as 65000
Hub Site 2, has the same configuration, except for local ip address and router BGP ID.
Spoke site:
interface Tunnel200
ip address 10.99.99.3 255.255.255.0
no ip redirects
ip mtu 1400
ip nhrp authentication auth
ip nhrp map 10.99.99.1 PUBLIC_IP_HUB_1
ip nhrp map 10.99.99.16 PUBLIC_IP_HUB_2
ip nhrp network-id 12345
ip nhrp holdtime 600
ip nhrp nhs 10.99.99.1 priority 1
ip nhrp nhs 10.99.99.16 priority 5
ip nhrp nhs fallback 60
tunnel source GigabitEthernet0/0
tunnel mode gre multipoint
tunnel key 200
tunnel protection ipsec profile dmvpn
interface GigabitEthernet0/1
description Internal
ip address 192.168.3.1 255.255.255.192
router bgp 99010
bgp log-neighbor-changes
network 192.168.3.0
neighbor 10.99.99.1 remote-as 65001
neighbor 10.99.99.16 remote-as 65013
On this spoke site
#sh ip route
B 192.168.1.0/24 [20/0] via 10.99.99.1, 00:47:01
which is the HUB network, but the rest of the MPLS routes are not "learned".
What am I missing?
Thanks!Hi Jon, I've ommited the configuration of the MPLS provider routers in between. The DC is connected to a router that has the AS 65510.
DC:CPE---PE:{MPLS}PE---CPE:HUB---{internet}---Spoke
The DC is ok getting the network information via BGP:
#sh ip route
B 192.168.3.0/24 [20/0] via 192.168.0.33, 3d05h
B 192.168.21.0/24 [20/0] via 192.168.0.33, 3d05h
#sh ip bgp 192.168.21.0
BGP routing table entry for 192.168.21.0/24, version 559
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 1
65510 3549 6140 3549 65000
192.168.0.33 from 192.168.0.33 (###.###.###.###)
Origin IGP, localpref 100, valid, external, best
#sh ip route 192.168.21.0
Routing entry for 192.168.21.0/24
Known via "bgp 65511", distance 20, metric 0
Tag 65510, type external
Last update from 192.168.0.33 3d05h ago
Routing Descriptor Blocks:
* 192.168.0.33, from 192.168.0.33, 3d05h ago
Route metric is 0, traffic share count is 1
AS Hops 5
Route tag 65510
MPLS label: none
Spoke:
#sh ip bgp
BGP table version is 494, local router ID is 192.168.21.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,
x best-external, a additional-path, c RIB-compressed,
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found
Network Next Hop Metric LocPrf Weight Path
*> 10.0.129.32/27 10.99.99.16 0 65013 65012 3549 ?
*> 192.168.96.0 10.99.99.16 0 65013 65012 3549 6745 65510 ?
#sh ip route 192.168.96.0
Routing entry for 192.168.96.0/24
Known via "bgp 99001", distance 20, metric 0
Tag 65013, type external
Last update from 10.99.99.16 00:02:11 ago
Routing Descriptor Blocks:
* 10.99.99.16, from 10.99.99.16, 00:02:11 ago
Route metric is 0, traffic share count is 1
AS Hops 5
Route tag 65013
MPLS label: none
#sh ip bgp 192.168.96.0
BGP routing table entry for 192.168.96.0/24, version 465
Paths: (1 available, best #1, table default)
Not advertised to any peer
Refresh Epoch 2
65013 65012 3549 6745 65510
10.99.99.16 from 10.99.99.16 (10.2.16.1)
Origin incomplete, localpref 100, valid, external, best
The route is not being updated to the rest of the routers, and the 192.168.21.0 network is still announced via the old route.
(from spoke)
ping 192.168.96.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.96.2, timeout is 2 seconds:
Success rate is 0 percent (0/5)
From DC
#traceroute 192.168.21.1
Type escape sequence to abort.
Tracing the route to 192.168.21.1
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.0.33 [AS 65510] 0 msec 0 msec 0 msec
2 172.50.1.33 [AS 65510] 56 msec 36 msec 36 msec
3 10.80.1.1 [AS 3549] 44 msec 44 msec 44 msec
4 10.80.1.2 [AS 3549] 172 msec 172 msec 168 msec
5 172.50.1.1 [AS 3549] 168 msec 168 msec 172 msec
6 172.50.1.2 [AS 3549] 180 msec 180 msec 176 msec
7 192.168.0.2 [AS 65000] 172 msec 172 msec 168 msec <- old route, should be 192.168.0.9
8 192.168.0.2 [AS 65000] !H * !H -
Route advertisement with AS path
Hello
We are running Multi-homed network, to influence the BGP route selection, we are using AS path attribute with route-maps.
Recently, we observed that the routes advertised on TCL network(ISP 1) were not reflected in global routing table.
For example, we have advertised a network (196.X.X.X/24) on TCL BGP peer as best path and also advertised the same network on another BGP peer with AS path pretend of 10times. But, the network is reaching via Bharti BGP (iSP 2 )peer instead of TCL peer.
Can anyone help understand as why it is preferred route is via Bharti
Thanks
Viswa SaiNetwork statement in BGP configuration is used to identify which networks are being advertised. BGP process then checks the global routing table, if it sees a prefix in global routing table and with exact match (including subnet mask), only then it will advertise that network to other BGP peers.
Is this network a local network or learned from other routing protocols? If locak, make sure you enter exact mask of the network seen in routing table. If learned from other routing protocols, the better way is to selectively redistribute iGP routes into BGP using prefix-list and route-map.
As far as convergence is concerned, below is explanation:
BGP routers router will not start the BGP Best-Path calculation/selection process until they receives all NLRI from BGP peer. This will be known from UPDATE messages. End of UPDATE messages is usually identified after a KEEPALIVE message is received.
The time taken to learn new best path is directly proportional to number of NLRIs received from peers.
Only when your service provider router selects it's best path, and installs into RIB, it is going to send UPDATE message to your routers. If SP routers use line cards with Cisco distributed forwarding, it is going to populate it's FIB and then send UPDATE message.
It depends on how fast your Bharati BGP peer detects your network unreachable and sends UPDATE messages to it's peers to withdraw your network's NLRI from it's routing table.
There are ways to improve this convergence, but at service provider level. In your network, if you want faster re-convergence, static routes (with higher AD) would be a wonderful solution.
Few other ways would be to use:
Bidirectional forwarding detection (BFD)
fast neighbor failover
BGP next hop tracking
BGP best external path (IOS and vendor specific)
BGP prefix convergence (IOS and vendor specific)
Peace and Health,
Ravindra -
Query on BGP route distribution
Hello Everyone
In the below scenario (GNS3), IBGP peering enabled between R1-R2, R1-R3, R2-R3 and EBGP peering enabled between R2-R4,R3-R5,R4-R6,R5-R7. OSPF enabled as IGP. Scenario attached for reference.
The problem I've observed in R1 is not getting entire BGP routing table for destinations 30.x.x.x/40.x.x.x.
I'm able to see only best routes in R1 BGP routing table, but alternate valid routes are not visible in its topology table.
R1#sh ip bgp
BGP table version is 81, local router ID is 100.100.2.1
*>i30.30.1.0/24 10.10.1.2 0 100 0 200 300 ?
*>i30.30.2.0/24 10.10.1.2 0 100 0 200 300 ?
*>i40.40.1.0/24 10.10.2.2 0 100 0 200 400 i
*>i40.40.2.0/24 10.10.2.2 0 100 0 200 400 i
*> 100.100.1.0/24 0.0.0.0 0 32768 i
*> 100.100.2.0/24 0.0.0.0 0 32768 i
More confusing part to me is when I disable IBGP peering between R2-R3 or shutdown interface between R2-R3 or else if I disable ospf in R1,R2 & R3 routers , I'm able to see both best route and alternate valid route in BGP topology table.
R1#sh ip bgpHi Milin & Renan,
Thanks for your replies. To narrow down the problem, I’ve shut down the 40.40.x.x network.
Now between R2-R3, R3 is not advertising 30.30.X.X network to R2, but whereas R2 is advertising 30.30.X.X network to R3. Why R3 is not advertising 30.30.X.X (route via 200 400 300) to R2.
R2#sh ip bgp ( No alternate route)
Network Next Hop Metric LocPrf Weight Path
*> 30.30.1.0/24 10.10.4.2 0 200 300 ?
*> 30.30.2.0/24 10.10.4.2 0 200 300 ?
*>i100.100.1.0/24 10.10.1.1 0 100 0 i
*>i100.100.2.0/24 10.10.1.1 0 100 0 i
R2#sh ip bgp summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.10.1.1 4 100 96 98 5 0 0 01:05:50 2
10.10.3.2 4 100 98 100 5 0 0 01:05:54 0
10.10.4.2 4 200 100 98 5 0 0 01:05:39 2
R3#sh ip bgp ( only in R3 we can see both best route & alternate route)
Network Next Hop Metric LocPrf Weight Path
*>i30.30.1.0/24 10.10.3.1 0 100 0 200 300 ?
* 10.10.5.2 0 200 400 300 ?
*>i30.30.2.0/24 10.10.3.1 0 100 0 200 300 ?
* 10.10.5.2 0 200 400 300 ?
*>i100.100.1.0/24 10.10.2.1 0 100 0 i
*>i100.100.2.0/24 10.10.2.1 0 100 0 i
R3#sh ip bgp summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.10.2.1 4 100 54 57 19 0 0 00:50:17 2
10.10.3.1 4 100 62 60 19 0 0 00:27:22 2
10.10.5.2 4 200 58 58 19 0 0 00:50:08 2 -
Hello,
i have this bgp topology all router running bgp and no igp is running. Now, the problem is R2 and R3 are route reflector, R1 and R4 are Rclient.
R3 has learn route from R4 (4.4.4.4) from its R client and it advertise to R2 but R2 not advertise (4.4.4.4) route to its client (R1).
R1#sh ip bgp
BGP table version is 5, local router ID is 192.168.12.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
*>i2.2.2.2/32 192.168.12.2 0 100 0 i
* i3.3.3.3/32 192.168.23.3 0 100 0 i
R2#sh ip bgp
BGP table version is 8, local router ID is 192.168.12.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i1.1.1.1/32 192.168.12.1 0 100 0 i
*> 2.2.2.2/32 0.0.0.0 0 32768 i
*>i3.3.3.3/32 192.168.23.3 0 100 0 i
* i4.4.4.4/32 192.168.34.4 0 100 0 iR3#sh ip bgp
BGP table version is 8, local router ID is 192.168.23.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i1.1.1.1/32 192.168.12.1 0 100 0 i
*>i2.2.2.2/32 192.168.23.2 0 100 0 i
*> 3.3.3.3/32 0.0.0.0 0 32768 i
*>i4.4.4.4/32 192.168.34.4 0 100 0
R3#sh run | se router bgp
router bgp 1
no synchronization
bgp log-neighbor-changes
network 3.3.3.3 mask 255.255.255.255
neighbor 192.168.23.2 remote-as 1
neighbor 192.168.23.2 next-hop-self
neighbor 192.168.34.4 remote-as 1
neighbor 192.168.34.4 route-reflector-client
no auto-summary -
I have two routers with BGP configured:
C2921:
router bgp 65014
bgp router-id 192.168.54.190
bgp log-neighbor-change
neighbor 192.168.54.150 remote-as 65011
neighbor 192.168.54.150 description Loud backup
neighbor 192.168.54.150 route-map Backup out
C1841:
router bgp 65011
no synchronization
bgp router-id 10.10.35.1
bgp log-neighbor-changes
neighbor 192.168.54.149 remote-as 65014
neighbor 192.168.54.149 description Cubus backup
neighbor 192.168.54.149 prefix-list Loudenia out
neighbor 192.168.54.149 route-map Backup out
ip prefix-list Loudenia seq 5 permit 10.10.35.0/24 le 32
ip prefix-list Loudenia seq 10 permit 192.168.111.0/24 le 32
ip prefix-list Loudenia seq 15 permit 10.25.15.0/24 le 32
ip prefix-list Loudenia seq 20 permit 192.168.44.0/24 le 32
ip prefix-list Loudenia seq 25 permit 192.168.45.0/24 le 32
ip prefix-list Loudenia seq 30 permit 192.168.46.0/28 le 32
ip prefix-list Loudenia seq 35 permit 192.168.49.196/30 le 32
ip prefix-list Loudenia seq 40 permit 192.168.49.225/32
ip prefix-list Loudenia seq 45 permit 192.168.49.229/32
route-map Backup permit 10
set as-path prepend 65011 65011
I have added:
ip prefix-list Loudenia seq 50 permit 192.168.48.225/32
made:
clear ip bgp 192.168.54.149 soft
but nothing changed route to 192.168.48.225 not advertised:
C1841-Loudenia#show ip bgp neighbors 192.168.54.149 advertised-routes
BGP table version is 137998, local router ID is 10.10.35.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 10.10.35.0/24 0.0.0.0 0 32768 i
*> 10.25.15.0/24 192.168.111.10 0 32768 i
*> 192.168.44.0 192.168.49.26 0 65005 i
*> 192.168.45.0 192.168.49.26 0 65005 i
*> 192.168.46.0/28 192.168.49.26 0 65005 i
*> 192.168.49.196/30
192.168.49.26 0 65005 i
*> 192.168.49.225/32
192.168.49.26 0 0 65005 i
*> 192.168.49.229/32
192.168.49.26 0 65005 i
*> 192.168.111.0 0.0.0.0 0 32768 i
C1841 knows 192.168.48.225/32 via bgp
* 192.168.48.225/32
192.168.49.58 0 65005 65005 65005 65006 65013 i
*> 192.168.49.26 0 65005 65006 65013 i
I will be grateful for your adviceThat is you mean?
C1841 knows 192.168.48.225/32 via bgp
* 192.168.48.225/32
192.168.49.58 0 65005 65005 65005 65006 65013 i
*> 192.168.49.26 0 65005 65006 65013 i -
What do we need to do if BGP Router contribute high process in CPU?
CPU utilization for five seconds: 97%/43%; one minute: 99%; five minutes: 92%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
44 36270732 35464661 1022 25.03% 15.21% 14.43% 0 BGP Router
325 7703860203228294256 0 10.47% 5.58% 5.24% 0 IP Input
455 7596596 28244228 268 5.59% 1.60% 0.82% 0 BGP I/O
543 13576608 8569950 1584 3.83% 18.94% 9.57% 0 BGP Task
9 152474380 15201602 10030 2.07% 0.27% 0.57% 0 Check heaps
376 16372652 7777145 2105 1.83% 13.93% 13.76% 0 IP RIB Update
358 56785192 14452691 3929 0.95% 0.44% 0.52% 0 CEF: IPv4 proces
23 55656604 116191071 479 0.71% 0.51% 0.50% 0 ARP Input
348 5736736 7812055 734 0.63% 4.19% 5.03% 0 XDR mcast
546 36531108 132425650 275 0.63% 0.37% 0.28% 0 Port manager per
35 56337684 306101724 184 0.23% 0.42% 0.30% 0 IPC Seat Manager
330 287962916 871459868 330 0.23% 0.39% 1.61% 0 SNMP ENGINE
286 7682841067821917 0 0.15% 0.07% 0.07% 0 Ethernet Msec Ti
626 354112 825565 428 0.15% 0.11% 0.09% 0 IPv6 Input
3 754316 523105917 1 0.15% 0.10% 0.09% 0 HSRP Common
385 2182508 14151135 154 0.15% 0.10% 0.14% 0 L3 Manager
317 44655884 658073408 67 0.07% 0.04% 0.21% 0 PDU DISPATCHER
395 4363480 4661440 936 0.07% 0.04% 0.05% 0 HIDDEN VLAN Proc
323 1161648 134374319 8 0.07% 0.04% 0.05% 0 VRRS Main thread
56 2269676 9230664 245 0.07% 0.08% 0.07% 0 Per-Second Jobs
240 1449416 1870109 775 0.07% 0.04% 0.05% 0 Compute load avg
243 1488814081309230003 113 0.07% 0.13% 0.76% 0 IP SNMP
CPU utilization for five seconds: 97%/43%; one minute: 99%; five minutes: 92%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
44 36270732 35464661 1022 25.03% 15.21% 14.43% 0 BGP Router
325 7703860203228294256 0 10.47% 5.58% 5.24% 0 IP Input
455 7596596 28244228 268 5.59% 1.60% 0.82% 0 BGP I/O
543 13576608 8569950 1584 3.83% 18.94% 9.57% 0 BGP Task
9 152474380 15201602 10030 2.07% 0.27% 0.57% 0 Check heaps
376 16372652 7777145 2105 1.83% 13.93% 13.76% 0 IP RIB Update
358 56785192 14452691 3929 0.95% 0.44% 0.52% 0 CEF: IPv4 proces
23 55656604 116191071 479 0.71% 0.51% 0.50% 0 ARP Input
348 5736736 7812055 734 0.63% 4.19% 5.03% 0 XDR mcast
546 36531108 132425650 275 0.63% 0.37% 0.28% 0 Port manager per
35 56337684 306101724 184 0.23% 0.42% 0.30% 0 IPC Seat Manager
330 287962916 871459868 330 0.23% 0.39% 1.61% 0 SNMP ENGINE
286 7682841067821917 0 0.15% 0.07% 0.07% 0 Ethernet Msec Ti
626 354112 825565 428 0.15% 0.11% 0.09% 0 IPv6 Input
3 754316 523105917 1 0.15% 0.10% 0.09% 0 HSRP Common
385 2182508 14151135 154 0.15% 0.10% 0.14% 0 L3 Manager
317 44655884 658073408 67 0.07% 0.04% 0.21% 0 PDU DISPATCHER
395 4363480 4661440 936 0.07% 0.04% 0.05% 0 HIDDEN VLAN Proc
323 1161648 134374319 8 0.07% 0.04% 0.05% 0 VRRS Main thread
56 2269676 9230664 245 0.07% 0.08% 0.07% 0 Per-Second Jobs
240 1449416 1870109 775 0.07% 0.04% 0.05% 0 Compute load avg
243 1488814081309230003 113 0.07% 0.13% 0.76% 0 IP SNMPHi,
BGP Router process is in charge to determine the best path and processes any route "churn". It also sends and receives routes, establishes peers, and interacts with the routing information base (RIB).
(http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/107615-highcpu-bgp.html)
So I suggest to check what make this process working hard. Depending on that you can choose what to do: bgp dampening (if you have many changes in advertisement received form a neighbor), tuning timer (if neighbor is flapping), using peer-group / update-groups to reduce the amount of job your BGP process has to do to process updates etc...
Have a look here: https://supportforums.cisco.com/discussion/11604471/high-cpu-usage-bgp-router-process
Bye,
enrico
PS please rate if useful -
Dual homed bgp route perference help
Good Morning, sir
I have a question regarding bgp route preference.
We have multi-homed BGP on remote site.
Let's call this site , site_a has verizon and at&t MPLS connection using bgp.
Currently, at&t route is preferred using as path prepend method.
We have addition AS number prepended on link to Verizon to prefer at&t route.
At this time, verizon is idle and not being used.
We would like to utilize this network to pass backup traffic.
We have source and destination address that we would like to pass through Verizon (out backup) link.
Any idea how I can do this?
I created the source/destination with ACL and created route-map matching that ACL and tweaked the local preference.
and since only major route is listed under 'show ip bgp' and not the specific route which I would like to influence,
I didn't see the tweaked route on routing table.
Any idea, anyone?
ThanksGetting the specific route into the routing depends on what is there ie. -
if there is already a route with same prefix and subnet mask in your IP routing table then you are fine.
If there isn't and your routing table does not have even more specific routes covering the whole subnet you want to advertise then you could use a static route either pointing to the next hop IP or the interface on the router used to get to that subnet.
Then you can use a "network ..." statement under your BGP configuration to advertise it and use a route map to only advertise it down the backup link.
Jon -
How to stop isp1 routes advertisement via isp2 on Bgp...
The problem is when my spoke isp1 mpls down...
Still it is getting routes via isp2I do not have an understanding of your topology or of the relationship between ISP 1 and ISP 2 and therefore can not be sure how well my suggestion will work. But here is what I frequently use when I want to be sure that routes learned from ISP 1 do not get advertised to ISP 2.
ip as-path access-list 10 permit ^$
router bgp 123
neighbor 1.2.3.4 filter-list 10 out
HTH
Rick
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