BGP load sharing ?

Hi,
got a customers who's connected to one of our PE using 2 links.
2 BGP sessions have been set (we can't peer on loopbacks), the ebgp multipath option is set, I seen the same routes twice with equal cost on my PE, but customers report that one link is at 80% of usage whereas the other rarely goes up to 20%.
Cef is configue "per destination".
Can't see why I have this behaviour except that someone on customer routeur is running heavy traffic TCP soft like P2P.
Are there some caveheats on "loadsharing" with BGP on MPLS VPN architectures ?
Thanks

Hi,
did you see 2 IP routes on remote PEs as well?
You might run into one problem coming from BGP maximum path for iBGP being 1 by default.
So you could try
router bgp 65000
addressfamily ipv4 vrf MyVRF
maximum-path ibgp 2
on all REMOTE PE, as they are learning the redundant CE routes through iMBGP and will not install both into the VRF routing table.
If you have route reflectors in place, then you will need to have different RD on the two VRFs the redundant CE interfaces are bound to.
Additionally on all remote PEs:
router bgp 65000
addressfamily ipv4 vrf MyVRF
maximum-path ibgp 2 import 2
egards
Martin

Similar Messages

BGP load sharing with bandwidth

We are running eBGP between two routers. We had a 250 M PVC between the two routers on OSM STM4 ATM interface. We need to increase the B/W between the two routers to 350M, but because there's a limitation on the PVC size for the OSM STM4 ATM card (Max. size of the PVC is 300M), so we created new PVC between the two routers on the same circuits (and of course the same interfaces). Now I need to enable the load sharing between the two routers taking the PVC B/W in consideration.. So I prepared this config, is it right and full? Or Am I missing anything here..
RouterA:
Router bgp 100
Neighbor 10.1.1.1 remote-as 200 (10.1.1.1 is loop back address fro Router B)
Neighbor 10.1.1.1 ebgp-multihop
bgp dmzlink-bw
neighbor 10.1.1.1 dmzlink-bw
neighbor 10.1.1.1 send-community both
maximum-paths ebgp 2
RouterB:
Router bgp 100
Neighbor 10.10.1.1 remote-as 200 (10.10.1.1 is loop back address fro Router A)
Neighbor 10.10.1.1 ebgp-multihop
neighbor 10.10.1.1 send-community both
bgp dmzlink-bw
neighbor 10.10.1.1 dmzlink-bw
maximum-paths ebgp 2

I implmented these changes but did not work, becuase the command neighbor 10.10.1.1 dmzlink-bw is not supported with multihop (Neighbor 10.10.1.1 ebgp-multihop).
I removed the loopback BGP neighbor and created 2 BGP neighbors with the directly connected interfaces IP's and applied same configuration and now it works fine.. Here's show Ip route (Ip's and AS numbers have been chnaged)
R1#sh ip ro 10.10.0.1
Routing entry for 10.10.0.0/20
Known via "bgp xxxxx", distance 20, metric 10
Tag xxxx, type external
Last update from x.x.x.x 00:00:24 ago
Routing Descriptor Blocks:
* x.x.x.x, from x.x.x.x, 00:00:24 ago
Route metric is 10, traffic share count is 240
AS Hops 1
Route tag xxxxx
y.y.y.y, from y.y.y.y, 00:00:24 ago
Route metric is 10, traffic share count is 83
AS Hops 1
Route tag xxxx
notice the traffic share count
traffic share count is 240 (for peer #1)
traffic share count is 83 (for peer # 2)
It's almost 3:1

BGP - Load sharing - q

My server LAN is – 172.30.1.0/24 , and using BGP for primary and secondary Links on a single HUB Router,
I need to Load share the secondary Link by specific ip address ,
172.30.1.5 and 172.30.1.6 server traffic only via the Secondary Link using BGP on Router.
Note : When secondary is down it should use primary Link for all my spoke sites
Need help what to change on HUB and spoke Router BGP configs

I agree with Rick, some more details would be helpful. However from your description it sounds as though you have a hub with multiple spokes and you are exchanging routes between them using BGP. You want traffic between the spokes and hub for the specific server IPs you provided to use the secondary link ?
If so the problem you have trying it with BGP is the return traffic. ie. you could advertise the server IPs as host addresses from the hub site down both links and use AS prepending so the secondary link was preferred at all spoke sites. All spokes would then use the secondary link to send traffic to these servers.
The issue with that though is when the servers reply the destination IP is one of the spokes site addresses. How are you going to make sure that the secondary link is used for this traffic. You cannot tell the hub router to use the secondary for all spoke addresses because then all return traffic would go via the secondary link ie. all return traffic being for any device sending traffic back to the spokes.
So i don't think BGP is the solution to this or it could only be a partial solution. PBR could solve the problem of the return traffic though so you could either -
1) use PBR on the hub router and PBR for all the spoke routers. This would be quite a lot of config as you would need to update all routers.
or
2) use BGP to make sure the spokes use the secondary link for traffic to the specific servers and then use PBR on the hub to make sure traffic from these specific servers uses the secondary link. The advantage of this would be all the configuration would only be on the hub router.
If you do use PBR you may also need to track the availability of the link so that if it failed it would failover to the other link.
Having said that, Rick may know of a better way to do this though, so some more specifics would be helpful.
Jon

MP-BGP and MPLS multipath load sharing

Hi,
I am trying to PoC MPLS multi path load sharing by using per-PE-per-VRF RDs in the network.
I have a simple lab setup with AS65000 which consists of SITE1 PE1&PE2 routers (10.250.0.101 and 10.250.0.102), route reflector RR in the middle (10.250.0.55) and SITE2 PE1&PE2 routers (10.250.0.201 and 10.250.0.202). PE routers only do iBGP peering with centralized route reflector and passing route to 10.1.1.0/24 prefix (learned from single CE router) with 100:1 and 100:2 RDs for specific VRF.
Route reflector gets routes with multiple RDs, makes copies of these routes in order to make local comparison to RD 55:55 configured, uses these routes and install multiple paths into its routing table (all PE routers and RR have "maximum-paths eibgp 4" configured):
RR#sh ip bgp vpnv4 all
BGP table version is 7, local router ID is 10.250.0.55
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
Route Distinguisher: 55:55 (default for vrf VRF-A) VRF Router ID 10.250.0.55
* i10.1.1.0/24      10.250.0.102             0    100      0 65001 i
*>i                 10.250.0.101             0    100      0 65001 i
Route Distinguisher: 100:1
*>i10.1.1.0/24      10.250.0.101             0    100      0 65001 i
Route Distinguisher: 100:2
*>i10.1.1.0/24      10.250.0.102             0    100      0 65001 i
RR#sh ip route vrf VRF-A
<output omitted>
     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
B       10.1.1.0/24 [200/0] via 10.250.0.102, 00:45:52
                          [200/0] via 10.250.0.101, 00:46:22
BUT, for some reason RR doest reflects routes with multiple RDs down to SITE2 PE1&PE2 - its own clients:
RR#sh ip bgp vpnv4 all neighbors 10.250.0.201 advertised-routes
Total number of prefixes 0
RR#sh ip bgp vpnv4 all neighbors 10.250.0.202 advertised-routes
Total number of prefixes 0
Here comes RR BGP configuration:
router bgp 65000
no synchronization
bgp router-id 10.250.0.55
bgp cluster-id 1.1.1.1
bgp log-neighbor-changes
neighbor 10.250.0.101 remote-as 65000
neighbor 10.250.0.101 update-source Loopback0
neighbor 10.250.0.101 route-reflector-client
neighbor 10.250.0.101 soft-reconfiguration inbound
neighbor 10.250.0.102 remote-as 65000
neighbor 10.250.0.102 update-source Loopback0
neighbor 10.250.0.102 route-reflector-client
neighbor 10.250.0.102 soft-reconfiguration inbound
neighbor 10.250.0.201 remote-as 65000
neighbor 10.250.0.201 update-source Loopback0
neighbor 10.250.0.201 route-reflector-client
neighbor 10.250.0.201 soft-reconfiguration inbound
neighbor 10.250.0.202 remote-as 65000
neighbor 10.250.0.202 update-source Loopback0
neighbor 10.250.0.202 route-reflector-client
neighbor 10.250.0.202 soft-reconfiguration inbound
no auto-summary
address-family vpnv4
neighbor 10.250.0.101 activate
neighbor 10.250.0.101 send-community both
neighbor 10.250.0.102 activate
neighbor 10.250.0.102 send-community both
neighbor 10.250.0.201 activate
neighbor 10.250.0.201 send-community both
neighbor 10.250.0.202 activate
neighbor 10.250.0.202 send-community both
exit-address-family
address-family ipv4 vrf VRF-A
maximum-paths eibgp 4
no synchronization
bgp router-id 10.250.0.55
network 10.255.1.1 mask 255.255.255.255
exit-address-family
SITE1 PE1 configuration:
router bgp 65000
no synchronization
bgp router-id 10.250.0.101
bgp log-neighbor-changes
neighbor 10.250.0.55 remote-as 65000
neighbor 10.250.0.55 update-source Loopback0
neighbor 10.250.0.55 soft-reconfiguration inbound
no auto-summary
address-family vpnv4
neighbor 10.250.0.55 activate
neighbor 10.250.0.55 send-community both
exit-address-family
address-family ipv4 vrf VRF-A
neighbor 10.1.101.2 remote-as 65001
neighbor 10.1.101.2 activate
neighbor 10.1.101.2 soft-reconfiguration inbound
maximum-paths eibgp 4
no synchronization
bgp router-id 10.250.0.101
exit-address-family
SITE1 PE2 configuration is similar to SITE1 PE1. They both do eBGP peering with dualhomed CE router in AS65001 which announces 10.1.1.0/24 prefix into VRF-A table.
My question is: clearly, the issue is that RR doesn't reflect any routes to its clients (SITE2 PE1&PE2) for 10.1.1.0/24 prefix with 100:1 and 100:2 RDs that dont match it's locally configured RD 55:55 for VRF-A, although they are present in its BGP/RIB tables and used for multipathing. Is this an expected behavior or some feature limitation for specific platform or IOS version? Currently, in this test lab setup I run IOS 12.4(24)T8 on all the devices.
Please, let me know if any further details are needed to get an idea of why this well known and widely used feature is not working correctly in my case. Thanks a lot!
Regards,
Sergey

Hi Ashish,
I tried to remove VRF and address family configurations completely from RR.
router bgp 65000
no synchronization
bgp router-id 10.250.0.55
bgp cluster-id 1.1.1.1
bgp log-neighbor-changes
neighbor 10.250.0.101 remote-as 65000
neighbor 10.250.0.101 update-source Loopback0
neighbor 10.250.0.101 route-reflector-client
neighbor 10.250.0.101 soft-reconfiguration inbound
neighbor 10.250.0.102 remote-as 65000
neighbor 10.250.0.102 update-source Loopback0
neighbor 10.250.0.102 route-reflector-client
neighbor 10.250.0.102 soft-reconfiguration inbound
neighbor 10.250.0.201 remote-as 65000
neighbor 10.250.0.201 update-source Loopback0
neighbor 10.250.0.201 route-reflector-client
neighbor 10.250.0.201 soft-reconfiguration inbound
neighbor 10.250.0.202 remote-as 65000
neighbor 10.250.0.202 update-source Loopback0
neighbor 10.250.0.202 route-reflector-client
neighbor 10.250.0.202 soft-reconfiguration inbound
no auto-summary
address-family vpnv4
neighbor 10.250.0.101 activate
neighbor 10.250.0.101 send-community both
neighbor 10.250.0.102 activate
neighbor 10.250.0.102 send-community both
neighbor 10.250.0.201 activate
neighbor 10.250.0.201 send-community both
neighbor 10.250.0.202 activate
neighbor 10.250.0.202 send-community both
exit-address-family
After this, RR doesn't accept any routes at all from S1PE1&S1PE2 routers, thus not reflecting any routes down to its clients S2PE1&S2PE2 as well:
S1PE1#sh ip bgp vpnv4 all
BGP table version is 6, local router ID is 10.250.0.101
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
Route Distinguisher: 100:1 (default for vrf VRF-A) VRF Router ID 10.250.0.101
*> 10.1.1.0/24      10.1.101.2               0             0 65001 i
S1PE1#sh ip bgp vpnv4 all neighbors 10.250.0.55 advertised-routes
BGP table version is 6, local router ID is 10.250.0.101
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
Route Distinguisher: 100:1 (default for vrf VRF-A) VRF Router ID 10.250.0.101
*> 10.1.1.0/24      10.1.101.2               0             0 65001 i
Total number of prefixes 1
S1PE2#sh ip bgp vpnv4 all
BGP table version is 6, local router ID is 10.250.0.102
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
Route Distinguisher: 100:2 (default for vrf VRF-A) VRF Router ID 10.250.0.102
*> 10.1.1.0/24      10.1.201.2               0             0 65001 i
S1PE2#sh ip bgp vpnv4 all neighbors 10.250.0.55 advertised-routes
BGP table version is 6, local router ID is 10.250.0.102
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
Route Distinguisher: 100:2 (default for vrf VRF-A) VRF Router ID 10.250.0.102
*> 10.1.1.0/24      10.1.201.2               0             0 65001 i
Total number of prefixes 1
RR#sh ip bgp vpnv4 all
RR#sh ip bgp vpnv4 all neighbors 10.250.0.101 routes
Total number of prefixes 0
RR#sh ip bgp vpnv4 all neighbors 10.250.0.102 routes
Total number of prefixes 0
Any feedback is appreciated. Thanks.
Regards,
Sergey

Configure bgp with load sharing

Hi,
We have 2 Lines to sprint on the same AS,
on our side we have 2 routers that running ebgp to sprint and ibgp between them.
now all the traffic go through one line only and if the primary line fail the traffic go through the backup.
we run eigrp on all our routers in all the sites and we have redestribute between bgp and eigrp also on the 2 routers that run ebgp to sprint.
we want to move to load sharing between those line base on sites , i mean some local soureces address will go through the backup line and the other go through the primary , same with the inbound traffic to those site&address .
what is the best way to do it, and how ?
Regards
Ronen.

you can only do load sharing. You cannot do load balancing because BGP selects only a single best
path to a destination among the BGP routes that are learned from the different ASs
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml

BGP requirements and load sharing

Hi !
I have been reading memory requirements for running BGP. But, for a tipical scenario with dual ISP for load sharing which are the requirements for the router ?
Could we use a 1841 or thinking about 37x5 or higher router ? I know that it depends on size for routing table, AS, and so on but what is the rule of thumb for choosing the correct router ?
Thanks
Rafa
http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml#conf2
Load Sharing When Dual-Homed to One Internet Service Provider (ISP) Through a Single Local Router
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a83.shtml
Achieve Optimal Routing and Reduce BGP Memory Consumption

Routes is one constraint and traffic is one more and the kind of policies i apply would be another. If i took a default from my upstream with about 1 MB of traffic, i would definitely look at 1841. If received routes ( atleast 20,000) and about 1 MB or 2 MB and 2 or more upstreams, I may even settle for a 3850.

Discussion on load-balance and load-sharing

Hi, I found a article, which discuss the difference between load-balance and load-sharing. I think the explanation is pretty good, please see below. But I still have a question: how can we decide to choose one the both balance in the production environment ? Thank you
"In short, load balancing tries to distribute traffic evenly over multiple paths, whereas, load sharing intends to do it (for the lack of a better term) equally. True load balancing is difficult to achieve. For example, let's say there were two links (100 mbps and 300 mpbs) and a router needed to send out 600 mbps of traffic. Load balancing would distribute the traffic evenly, sending 300 mbps on each link. On the contrary, load sharing would divide the traffic equally based on the available resources, sending 200 mbps on the slower link and 400 mbps on the faster one. "

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That's not how Cisco uses the terms, and generically they are often used almost interchangeably.
Cisco uses load balancing as the catch all for how a single L3 device routes across multiple paths to the same destination. Equal metrics or equal actual load distribution are not required. Most often, load balancing will be discussed with ECMP, but unequal path loading balancing will include Cisco's proprietary IGPs, such as EIGRP.
Cisco uses load sharing when using multiple paths when a single L3 devices doesn't normally route across multiple paths or multiple L3 devices are involved. Cisco load sharing discussions usually revolve around BGP.
Generically, I would say load balancing has more of a dynamic aspect to it, i.e. something is trying to actively balance traffic across multiple paths, while load sharing might mean multiple paths are utilized but not actively dynamically balanced.
I'm unsure what's your question with a production environment.

Load-balancing vs Load-sharing (L2/L3)

What is the difference in load balancing and load sharing. Can you generalize load-balancing to layer two? Or layer three protocols also do this, except BGP?
FHRPs like VRRP, GLBP, and HSRP are essentially load sharing protocols (except GLBP though). Loop prevention mechanisms like MSTP, G.8032, and REP also do not do load balancing I guess. Instead they offer a way to distribute (share) traffic over multiple links unevenly. Why do people still call it load-balancing?
While link aggregation may truly be considered load balancing. Where traffic can be balanced based on a few attributes ( src-dst/mac, ip, port).
And what role does fast-switching/process-switching play in load balancing. I am aware that these are the very processes that ultimately do load-balancing, given enough equal cost paths. Does CEF really take load balancing to another level? It still does the same job, but by caching flow data (RIB) to the CEF table, doesn't it?
Incase of IGP, load-balancing may be possible, but BGP just doesn't support it. Because it only selects one best route (?). Even with multipath, BGP advertises best path only; it does install multiple routes in routing table though. So IGP does the balancing?

What is the difference in load balancing and load sharing. Can you generalize load-balancing to layer two? Or layer three protocols also do this, except BGP?
FHRPs like VRRP, GLBP, and HSRP are essentially load sharing protocols (except GLBP though). Loop prevention mechanisms like MSTP, G.8032, and REP also do not do load balancing I guess. Instead they offer a way to distribute (share) traffic over multiple links unevenly. Why do people still call it load-balancing?
While link aggregation may truly be considered load balancing. Where traffic can be balanced based on a few attributes ( src-dst/mac, ip, port).
And what role does fast-switching/process-switching play in load balancing. I am aware that these are the very processes that ultimately do load-balancing, given enough equal cost paths. Does CEF really take load balancing to another level? It still does the same job, but by caching flow data (RIB) to the CEF table, doesn't it?
Incase of IGP, load-balancing may be possible, but BGP just doesn't support it. Because it only selects one best route (?). Even with multipath, BGP advertises best path only; it does install multiple routes in routing table though. So IGP does the balancing?

MPLS VPN load sharing when multihoming

Any one know of best practices for outbound load balancing when multihoming to 2 different service providers in an mpls vpn.
I have referred to this document (http://www.cisco.com/warp/public/459/40.html) which states the only way to do this is by assigning metrics/weights to a certain range of prefixes learned from one provider, hence load sharing.
Turning up bgp multipath on the CE would be optimal but since AS PATHs are different the best path selection will be different. Could we possibly turn of best path selection for AS paths (bgp bestpath as-path ignore) and make multipath work? Would that install 2 routes for the same prefix in the RIB?
Thanks
Ariful Huq

Yes you can turn off best path selection for AS path and have multipath work. For a route to be populated in routing table BGP has various metrics for its selection. AS path is one of the metrics it uses for best route selection, so I dont think there should be any problem with it.

CEF Load Sharing Recursive Lookup

Hi,
i have this scenario:
| ----P1----P2---|
PE1----| |----PE2
| ----P3----P4---|
IP Loop PE1: 5.5.5.5
There are 2 Gigabitethernet betweenn the router PE and the router P.
PE1 advertise 1.1.1.1/32 to PE2:
PE2#sh ip route 1.1.1.1
Routing entry for 1.1.1.1/32
Known via "bgp 65000", distance 200, metric 0, type internal
Last update from 5.5.5.5 01:57:03 ago
Routing Descriptor Blocks:
* 5.5.5.5, from 4.4.4.4 , 01:57:03 ago
Route metric is 0, traffic share count is 1
AS Hops 0, BGP network version 0
PE2 has 4 link (2 towards P2 and 2 towards P4) at equal cost to reach 5.5.5.5/32 via OSPF:
PE2# sh ip route 5.5.5.5
Routing entry for 5.5.5.5/32
Known via "ospf 65000", distance 110, metric 200, type inter area
Last update from 23.23.23.24 on GigabitEthernet8/0/0, 01:13:45 ago
Routing Descriptor Blocks:
* 22.22.22.21, from IP-P1, 01:13:45 ago, via GigabitEthernet3/0/0
Route metric is 200, traffic share count is 1
23.23.23.23, from IP-P1, 01:13:45 ago, via GigabitEthernet8/0/0
Route metric is 200, traffic share count is 1
22.22.22.22, from IP-P2, 01:13:45 ago, via GigabitEthernet3/0/0
Route metric is 200, traffic share count is 1
23.23.23.24, from IP-P2, 01:13:45 ago, via GigabitEthernet8/0/0
Route metric is 200, traffic share count is 1
If I look cef table I have all the 4 link too:
PE2# sh ip cef 5.5.5.5
5.5.5.5/32, version 3101050, epoch 0, per-destination sharing
0 packets, 0 bytes
Flow: AS 0, mask 32
tag information set, shared, all rewrites owned
local tag: 1541
via 22.22.22.21, GigabitEthernet3/0/0, 14 dependencies
traffic share 1
next hop 22.22.22.21, GigabitEthernet3/0/0
valid adjacency
tag rewrite with Gi3/0/0, 22.22.22.21, tags imposed {390}
via 23.23.23.23, GigabitEthernet8/0/0, 14 dependencies
traffic share 1
next hop 23.23.23.23, GigabitEthernet8/0/0
valid adjacency
tag rewrite with Gi8/0/0, 23.23.23.23, tags imposed {390}
via 22.22.22.22, GigabitEthernet3/0/0, 15 dependencies
traffic share 1
next hop 22.22.22.22, GigabitEthernet3/0/0
valid adjacency
tag rewrite with Gi3/0/0, 22.22.22.22, tags imposed {390}
via 23.23.23.24, GigabitEthernet8/0/0, 15 dependencies
traffic share 1
next hop 23.23.23.24, GigabitEthernet8/0/0
valid adjacency
tag rewrite with Gi8/0/0, 23.23.23.24, tags imposed {390}
0 packets, 0 bytes switched through the prefix
tmstats: external 0 packets, 0 bytes
internal 0 packets, 0 bytes
But if i Look the cef table for the address 1.1.1.1/32 I have only 1 link:
PE2# sh ip cef 1.1.1.1
1.1.1.1/32, version 6477717, epoch 0, per-destination sharing
0 packets, 0 bytes
Flow: AS 0, mask 32
tag information from 5.5.5.5/32, shared, all rewrites owned
local tag: 1541
via 5.5.5.5, 0 dependencies, recursive
next hop 22.22.22.22, GigabitEthernet3/0/0 via 5.5.5.5/32 (Default)
valid adjacency
tag rewrite with Gi3/0/0, 22.22.22.21, tags imposed {390}
Recursive load sharing using 5.5.5.5/32.
The question is: why PE2 doesn't utilize all the 4 link (towards P2 and P4) to reach 1.1.1.1/32?
Thanks in advance
Rgds
Gianluca

Although the "show ip cef 1.1.1.1" command only displays one interface, the recursive loadsharing will take place as expected.
Do a "show ip cef 1.1.1.1 internal", which will show you the 4 outbound interfaces being used.
Hope this helps,

BGP LOAD BALANCING

BGP chooses only a single best path to reach a specific destination. BGP is not designed to perform load balancing..
what i learned from every doc... but suppose this two ebgp neighbor have multiple path, creating neighborship by using loopback ip, to reach loopback router have 2 equal cost igp routes...in that case after recursive lookup router will load balance the traffic ...
Plzzz let me know am i right... or what is the meaning of this statement :
At one side it is said bgp is not made for load balancing specially in ccna, ccnp other exam books, but after doing google found following link, saying load balancing/load sharing can be done.... Why this confusion...
http://ccieblog.co.uk/bgp/bgp-unequal-load-cost-sharing
Please tell me what is truth...

Milan,
link will help me lot...
but...
The maximum-paths command for BGP works if your router has multiple parallel paths to different routers in the same remote AS; this command affects only the number of routes kept in the IP routing table, not the number of paths selected as best by BGP. For BGP, the paths parameter defaults to one.
Suppose R1 have 2 paths to reach any destination; Without the maximum-paths command under the router bgp, there is only one path in R1’s routing table. After the maximum-paths 2 command is added to the R1 BGP configuration, both paths appear in the IP routing table, However, only one path is still selected as the best in the BGP table.
Vasilii & Reza,
means what is right statement for bgp load balancing ....or is it changed case to case..?? please clear me...
Guies ...can you also tell me bgp support for "load balancing" & "load sharing"???

MPLS Traffic Load Sharing

What is the best way to configure a load sharing policy from multiple CE "remotes" to two CE "hosts" in a MPLS network? Currently, all incoming traffic goes to only one host from the PE.

Hi,
you need to have a look at the complete routing architecture to understand possibilities/responsibilities.
Mainly load distribution for a single prefix can only occur, if more than one path to a destination is known. This however might not be given in the MPLS network. The underlying reason is that BGP will only send the best path in an update - but not all pathes a BGP speaker knows of (RFC mandates this).
As practically all larger BGP implementations use Route Reflectors, which are (RFC conforming) BGP speakers, they will only forward the best path to a destination. The result is:
IF more than one path to a destination network exists and is sent to the RR through different PE routers (with same RD) then only one path will be distributed to all other PE routers.
In this scenario load sharing for a single prefix can not occur, because only one routing table entry exists for this prefix in most if not all PE routers. All you can do is to try to load share by selecting different pathes for different destination prefixes by influencing routing metric. This way part of your traffic will go one way and part will take another path.
IF the SP however uses different RD values for every VRF and the proper "maximum-path" statements in MP-BGP, then load sharing per prefix can be achieved in the MPLS network. The customer however can not influence the SP setup.
Hope this Helps! Please rate all posts.
Regards, Martin

Load sharing/balancing between 2 Service Providers

Hi,
I have a scenario where I have the following and this is repeated at different sites globally.
CE1-----------PE1_SP1---MPLS cloud
|
CE1---standby--PE2_SP1---MPLS cloud
CE2-----------PE1_SP2----MPLS Cloud
|
CE2---standby--PE2_SP2---MPLS Cloud
2 different service providers and we require load sharing/balancing to both SP1 and SP2.
If either of the SP's PE router is down it should bring up the standby link.
2 ASN, not sure if I can load share different prefixes in this scenario.
Will the applications fail?
Will the traffic flow be symmetric ?
Any help is very much appreciated.
Thanks,
Paul

Hello Paul,
if you are using a single CE router on each site.
to get load-balancing on your CEx:
router bgp X
maximum-paths 2
eBGP load-balancing is easier so 2 ISP ASN is fine
Verify that you have flow based load-balancing and everything should be fine.
Notice that you have a failure on site N of provider1 you can be able to detect it in all remote sites only if they are receiving the routes of all the sites. If receiving a default route there's no way for other sites to detect the failure.
If receiving all the prefixes after MP-BGP convergence in ISP1 site N's prefixes will be withdrawn and will be reachable only via ISP2.
To use an active/standby
on all Cex
router bgp x
neighbor PE-ISP1 weigth 500
neighbor PE-ISP1 fast-external-fallover
in this way until a prefix is present in ISP1 MP-BGP traffic is sent via ISP1
If using two CE in each site things are a little more complex and you need an iBGP session between them.
Hope to help
Giuseppe

BGP load balance

We are big ISP, and we are peering ebgp with several International ISPs for inetrnet connectivity. My question is how to load balance between the several ISPs, I mean based on what?, we need to make sure to load balance in both ways.

Hi,
usually load balancing has two parts:
1) local traffic to the internet
2) return traffic from the internet
As we are talking about BGP any mechanism influencing path selection can be used to load balance local traffic.
Basically you send traffic towards some destinations through one peering point and some traffic to other destinations through other peering points. Local Preference could be a good way to achieve this.
Be aware that you need some traffic analysis in order to influence the local traffic in the desired way.
Regarding option 2):
We are talking about BGP and what you want is to influence the routing decisions of other ASes. Bad news: there is no way to make SURE it will happen the way you want this to happen. They are AUTONOMOUS and therefore can also use f.e. LocPref to achieve their goals. Those might contradict yours.
But from a technical point of view the BGP updates you send should contain "hints" as to where the return traffic should be sent. As anything can be stripped of a BGP update except well-known mandatory attributes (origin, next-hop, AS path) usually AS path prepending is the measure to make return traffic for one of your prefixes prefer one way. And traffic for other prefixes you own another way.
Also be aware that BGP in itself was not built for Load sharing per prefix, because every BGP speaker will only announce the best path per prefix. So even in the neighbor AS after a route-reflector all BGP speakers will only learn ONE path to your AS per prefix.
Hope this helps
Martin
P.S.: Do not prepend too many ASes and do not split your IP address space in to many small junks. Also look at RIPE document 229, which talks about route flap dampening ... larger prefixes are always better.

Error while loading shared libraries: librt.so.1: cannot open shared object

error while loading shared libraries: librt.so.1: cannot open shared object
I cant run my apache server v2.2.3.
Can someone help me?
thanks in advance

That could be an accessibility issue. Check the user with whom you installed Apache server. Check the user has permissions to access the libraries.
-Mahendra.

BGP load sharing ?

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