EIGRP and BGP

when EIGRP and BGP is flapping.
which portion should I check to find out
if it is flapping because of high traffic or low quality access lines?
which should config should I check?
thanks a lot

Following links may help you
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094613.shtml
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a008009478a.shtml

Similar Messages

Cisco Nexus 5ks EIGRP and Policy routing question.

We just got installed a METRO LINK between our primary and secondary data center (Site-A <> Site-B) I would like to be able to route data replication between these two sites over that link, instead of going over MPLS. We run EIGRP internally and BGP to the MPLS (typical scenario)
At first I thought about doing ‘Policy Based Routing’ with IP SLA to be able to track and route traffic coming from the 10.10.10.0/24 bound to 10.11.11.0/24 and track link state with IP SLA in case the metro link would go down; data replication would continue to flow over MPLS.
In researching this, I found out that Cisco NX-5ks and 6Ks don’t support IP SLA and there is no telling if they will support it any time in future releases either.
I haven’t turned on routing (EIGRP) between the two 5ks over the metro link yet.
Also, I don’t want to statically route replication traffic over the link unless I have to. It would have to be a manual change in case I need to re-route it over the MPLS.
See attached drawing
Any help would be greatly appreciated.
Marramix01

can you calculate the metrics of the two different links for EIGRP?
Once you have that you would know which one EIGRP would say is the best path. Then if the MPLS link is not the primary path then you can use Offset-list to force the traffic to and from subnets and still have failover with EIGRP.
I hope I understood your problem correctly.

Question about network statement in OSPF and BGP

The network statements in OSPF and BGP can be used to advertise networks. But I'm not clear under what circumstances would make more sense to use network statements to advertise a network than by using other methods to have the network learned by other routers.
Here is an example: assume I'm running BGP on router A. I want to advertise network 10.1.1.0/24 to other BGP peers. I have a OSPF route for this network. I can do 2 things: one is to use "network 10.1.1.0 mask 255.255.255.0", the other is to do "redistribute OSPF ... route-map OSPF-INTO-BGP", and create a prefix list to permit 10.1.1.0/24.
Both would work to have this network learned by other BGP peers. But which is better for what purpose?
Thanks a lot
Gary

Hi Gary,
There is one little difference between the use of the two approaches - the route injected into BGP by using a network statement will carry an Origin attribute of IGP, whereas the route injected using redistribution will have an Origin attribute of Incomplete. Now, that is not a huge issue since you can always change that whatever value you desire both with the use of the network statement and redistribution. The important thing, however, is that in the BGP best path selection process, the Origin attribute comparison is fairly high up and will prefer a route with the attribute of IGP.
Apart from that, there is absolutely no difference between using the network statement and using redistribution with a route-map that matches exactly on the same route that you would have specified with the network statement.
I guess one advantage of using the redistribute approach is that it does not clutter up the BGP config. If you wish to add more routes, you simply add them to the prefix list so that you don't really touch the BGP config portion at all..
Hope that helps - pls do remember to rate posts that help.
Paresh

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 1

If 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

3850 and BGP

This is a fairly general question, but I have a stack of two 3850 switches with the IP Services IOS (or whatever its called now in IOS 15, it's the license that removes EIGRP stub) for a new deployment with Two ISP's. Both ISP's will hand us an Ethernet port, and we will peer with each ISP with BGP to advertise our address space (a single /22). We will receive a default route from one ISP, and a default route and the ISP's local routes from the other.
We originally planned to use two 2921 routers to peer with the ISP's, but I'm not sure thats necessary. Does BGP work pretty well on the 3850's in others experiences?

No NAT. As I stated above, we are only getting default routes and maybe one ISP's local routes, so the routing table size won't be an issue. If it does, I'll just accept default routes and that will be that.
All BGP features we currently use appear to be supported by the 3850, or at least it accepted the commands. Our config isn't anything special. Just curious about peoples impressions of BGP on the 3850's.
thanks!

Interview question: EIGRP and Grandmother

Hi all.
A question was asked to me a couple of months ago during an interview. I'm quite curious as to how others would respond to it. Here it is.
"If I was your grandmother, how would you make me understand EIGRP?"
I know that when the interviewer says "make me understand", it doesn't mean you should go deep into the details of the IGP. Maybe just a bird's eyeview. But still, makes you think.

I guess I'd have to relate it to something my grandmother would understand. I know she would be lost as soon as I said IP.
I would probably relate to driving in her car to get to the grocery store. Imagine if it every corner there was a traffic guard directing traffic, and every traffic guard had a map with the fastest way to get to her destination in his hand. When she gets to that intersection the traffic guard tells her which way to go. As long as all the roads are working the path she takes to the store pretty much remains the same. Now imagine that all of these guards have walkie-talkies in their hands, and if there is an accident on a road, and that road is closed that guard announces to all the other traffic guards that that road is closed and and the traffic guards are quickly able to give you an alternate route before you get stuck in traffic. The good thing about EIGRP is that these updates to traffic patterns are only sent periodically instead of all the time, this greatly reduces the amount of communication over the walkie-talkies, making it much easier for other communication to pass over them as well, while keeping everyone updated on what the best path to take to the store is.
I like trying to use analogies in my explanations to my end users. It puts the context of your discussion into terms that they can relate to and understand the general concept of. An interviewer might be asking you to do this to show, that you not only can regurgitate the answer that they're looking for, but understand it well enough to break it down into simpler terms that can be communicated to someone without technical knowledge that can still be understood.
I report to the VP of Finance/CFO here at my organization. I find myself constantly having break down complicated terms into something that he can understand in order to get budget approval for projects. I'm guessing your interviewer wanted to be sure you had the skills to be able to communicate complex IT concepts with someone who may not understand the "dictionary" explanation?

Best Practice Two ISPs and BGP

Hello Experts.
I was wanting to hear opinions for the best way to setup two ISR4431's with two 2960x's and two ASA firewalls.
My current design is:
ISP1 router -> ISR4431-A ->{2960x pair} -> ASA-A
ISP2 router -> ISR4431-B ->{2960x pair} -> ASA-B
Currently using public BGP and HSRP on the inside with an SLA monitor to a public IP.
If HSRP is the best way to accomplish this, how do i solve these two problems or is there a better design? (The two 4431's are not connected to each other currently.)
-Least Cost routing (i guess that is what its called) - I want to visit a website that is located on ISP2's network (or close to it), but HSRP currently has ISP1 as active. If i go out ISP1 it may go around the country or 10 hops before it hit a site that is 4 hops away on the other ISP.
-Assymetric routing - i think that is where a reply comes in the non-active ISP - how do i prevent that.
I am really just looking for design advice about the best way to use this hardware to create as much redundancy as possible and best performance possible. If you could just share your opinion of "I would use ____" or give me a stamp of reassurance on the above design and any opinion on the two problems.
Thanks for the time!

Hi,
If you are running BGP with the service provides, you need an IBGP link between the 2 ISR-4431 routers. If for example you want traffic to go out using sp-1 and come back using the same provider you need to us AS path prepending, so sp-2 sees a longer path to your network and so traffic goes out and comes back through the same provider. In this case you use sp-2 as backup link, if not you can be dealing with Asymmetric routing. In addition, for HSRP/VRRP to work both routers should be connecting to the set of 2960x switches. You can simply stack the 2960x switches so they logically look as one device. The same should go for the firewalls. They should connect to the switch stack.
HTH

EIGRP and Load Balacing Per Packet CEF required on both ends???

Here's what I have.
-2 T1's with same EIGRP metric
-CEF is enabled and load sharing currently
1 Link is being used more than the other due to nature of load sharing and not per packet using CEF.
I need per packet setup to see if this improves performance and distributes the usage over both links effectively.
If I enable per-packet on my remote office, do I also have to enable it on each PVC that connects back to my central office per PVC. Or can you enable per packet on the remote location only and be ok? I dont have control over central office router and need to justify if I need to enable that on the Central office or not.
Cisco docs I reviewed on this doesn't say both ends.

I agree with Sundar's point about needing to configure both ends if you want to use per packet in each direction. His point about the implications of forcing process switching and its impact on CPU utilization of the router is true but I am not sure that is what the original post was asking about. As I understood the original post he was asking about the per-packet option available with CEF switching which does not produce process switched packets.
I have one caution to offer about turning on the per-packet option with CEF. If you do that you will probably get better - but still not even - balancing of the serial links. But the performance may not improve. In fact it may degrade. This is because doing per packet balancing introduces the liklihood of out of order packets. The impact of out of order packets varies depending on the application being run and the impact of out of order packets. Many applications when they get an out of order packet will discard the packet and retransmit packets to get them in the correct order. I actually know of one customer site where they enabled per packet balancing and the performance of the application got worse. So I suggest that you evaluate carefully the implications of per packet balancing.
HTH
Rick

Direct Connect OSPF and BGP AWS failover setup

Hi,
We recently installed AWS Direct Connect which was successful but now we are looking at the best way to automatically fail over if our Direct Connect fails to route via our back VPN.
The setup
Cisco 6500 distributes routes via OSPF internally to all production environments with one area set.
A second Cisco 2901 was installed to support the AWS Direct Connect which uses BGP with a single ASN. This router is connected to the Cisco 6500 and now within the OSPF area. Static routes exist to the Cisco 2901 currently which unless we physically detach from the network fail over wont work.
What we want to achieve
The Cisco 2901 Direct Connect to be the default AWS route until we have a link issue or alike and dynamically fail over to our VPN via the firewall to AWS. What we are confused is do we advertise these BGP routes within OSPF or should we setup BGP on the Cisco 6500?
I appreciate your time.

Hi,
We recently installed AWS Direct Connect which was successful but now we are looking at the best way to automatically fail over if our Direct Connect fails to route via our back VPN.
The setup
Cisco 6500 distributes routes via OSPF internally to all production environments with one area set.
A second Cisco 2901 was installed to support the AWS Direct Connect which uses BGP with a single ASN. This router is connected to the Cisco 6500 and now within the OSPF area. Static routes exist to the Cisco 2901 currently which unless we physically detach from the network fail over wont work.
What we want to achieve
The Cisco 2901 Direct Connect to be the default AWS route until we have a link issue or alike and dynamically fail over to our VPN via the firewall to AWS. What we are confused is do we advertise these BGP routes within OSPF or should we setup BGP on the Cisco 6500?
I appreciate your time.

Tracing a route in EIGRP and null0

Hi Everyone,
Happy New Year!
I am checking if routing is there from source to Destination IP 172.23.7.110?
During tracing i reach one device along the path and did
sh ip route vrf RC   172.23.7.110
Routing entry for 172.23.0.0/16
Known via "eigrp 52", distance 5, metric 2816, type internal
Redistributing via eigrp 52
Routing Descriptor Blocks:
* directly connected, via Null0
      Route metric is 2816, traffic share count is 1
      Total delay is 10 microseconds, minimum bandwidth is 1000000 Kbit
      Reliability 255/255, minimum MTU 1500 bytes
      Loading 1/255, Hops 0
What should i do on this device so i can reach 172.23.7.110 from here?
Is it ok to put static route on this vrf RC?
Regards
Mahesh

Mahesh
The additional information that you posted for Jon does give us the reason for what you are observing. Under router eigrp you have configured auto-summary. Your configuration suggests that there are some interfaces in network 10.0.0.0. With auto-summary enabled when EIGRP is going to advertise out an interface in network 10.0.0.0 it will create a summary address for 172.23.0.0 and specify null 0 as the next hop.
Now that we understand where the summary route is coming from we can now begin to think about your other question - should you add a route for the address that you are trying to reach. As Jon has said we really need more information to be able to answer that question.
- should this router be able to reach that address?
- if so then how should this router learn that address?
- is the router where that address is located advertising that subnet?
- should the router where that address is located be advertising that subnet?
- is some device along the path dropping the advertisement or filtering out the advertisement?
When there are answers for those questions it will be easier to know whether you should add a route on this router.
HTH
Rick

EIGRP and DMZ distribution - Cisco ASA

I have been able to get EIGRP working successfully in the lab like I want.
Attached is the network overview:
We have a Data Center and Corporate office connected via Point to Point Fiber link, eventually we will have two of these
Two 4948E switches in the Data center acting as cores setup with GLBP
Corporate Office has a 3750X acting as a core
Currently two 4948E's are connected to each other via Port Channel and a L2 trunk
Two set of ASA 5520's one acting as a firewall and for Cisco Any Connect and second for site to site VPN
What is the best way/pratice that I can distribute this DMZ via EIGRP? Should I just leave it static on the core like this?
DMZ Net = 192.168.150.0/24
Inside Interface = 192.168.200.255
On the core I create a static route "ip route 192.168.150.0 255.255.255.0 192.168.200.255". Or a statement like this would be better for future DMZ additions "ip route 0.0.0.0 0.0.0.0 192.168.200.255"?

Hello Mohammad,
I would recommend you to advertise them via EIGRP, better funcionality, escalability,etc,etc,etc.
Regards

EIGRP and Distribute-list commands

I am reviewing one of our WAN routers, on an infrastructure I have recently inherated, and noted an EIGRP configuration which doesn't make much sense to me. I'm wondering if I misunderstand the intent. The WAN router has the following EIGRP configuration:
router eigrp 102
variance 4
redistribute connected
redistribute static
network 10.0.0.0
network 172.1.0.0
network 172.20.0.0
network 172.22.0.0
network 172.24.0.0
network 172.25.0.0
network 172.27.0.0
network 172.30.0.0
network 192.9.200.0
network 192.9.201.0
network 192.168.0.0
network 192.168.2.0
maximum-paths 2
default-metric 64 200 255 1 1500
distribute-list 20 out Serial3/0.41
distribute-list 20 out Serial3/0.76
distribute-list 20 out Serial3/0.100
distribute-list 20 out Serial3/0.104
distribute-list 20 out Serial3/0.106
distribute-list 20 out Serial3/0.107
distribute-list 20 out Serial3/0.111
distribute-list 20 out Serial3/0.112
distribute-list 20 out Serial3/0.113
distribute-list 20 out Serial3/0.117
distribute-list 20 out Serial3/0.118
distribute-list 20 out Serial3/0.131
distribute-list 20 out Serial3/0.170
distribute-list 20 out Serial3/0.175
distribute-list 20 out Serial3/0.186
distribute-list 20 out Serial3/0.190
distribute-list 20 out Serial3/0.191
distribute-list 20 out Serial3/0.198
distribute-list 20 out Serial3/0.199
distribute-list 20 out Serial3/0.205
distribute-list 20 out Serial3/0.210
distribute-list 20 out Serial3/0.226
distribute-list 20 out Serial3/0.251
distribute-list 20 out Serial3/0.621
distribute-list 20 out Serial3/0.629
distribute-list 20 out Serial3/0.637
distribute-list 20 out Serial3/0.647
distribute-list 20 out Serial3/0.658
distribute-list 20 out Serial3/0.663
distribute-list 20 out Serial3/0.677
distribute-list 20 out Serial3/0.696
distribute-list 20 out Serial3/0.700
distribute-list 20 out Serial3/0.719
distribute-list 20 out Serial3/0.733
distribute-list 20 out Serial3/0.762
distribute-list 20 out Serial3/0.763
distribute-list 20 out Serial3/0.771
distribute-list 20 out Serial3/0.772
distribute-list 20 out Serial3/0.776
distribute-list 20 out Serial3/0.783
distribute-list 20 out Serial3/0.801
distribute-list 20 out Serial3/0.803
distribute-list 20 out Serial3/0.810
distribute-list 20 out Serial3/0.822
distribute-list 20 out Serial3/0.830
distribute-list 20 out Serial3/0.832
distribute-list 20 out Serial3/0.853
distribute-list 20 out Serial3/0.855
distribute-list 20 out Serial3/0.880
distribute-list 20 out Serial3/0.915
distribute-list 20 out Serial3/0.1000
no auto-summary
eigrp log-neighbor-changes
However, access list 20 is constructed as follows:
access-list 20 permit 0.0.0.0
access-list 20 deny any
If you have a distribute-list statement within EIGRP but the ACL permits 0.0.0.0, does that make any incoming/outgoing updates passive in any way? The remote routers connected to the WAN have no passive/no passive configuration parameters. Only the core WAN routers do.
Please advise.

Marking a remote stub does not, today, restrict what routes are advertised to the stub router, they just limit the queries to the stub routers. So, you'd still need the hub side distribute list to block the routes out to the stubs. A distribute list doesn't block queries, by the way, it just limits knowledge of routing information, which impacts how far a query will go.... You should definitely make the remotes stubs to reduce the query range, in other words, even with this distribute list configured.
At any rate, there is a feature planned for the future to make it where you could turn on an option at the stub router to make the hub router automatically filter everything but the default out.
HTH....
Russ

New ARIN Block Transition and BGP Setup

Hello all,
First post on the forum so I bear with me. I am still young in my carrier and have not worked with BGP on a professional level.
We received a new IP Address block from ARIN and need to transition to it. The boss does not want to do a hard cut over but a phased migration instead. I need to know if this is possible and any configuration guides that might be handy.
Our current IP block is a /26 given to us by our ISP routing protocols are all handed by them we just use gateway of last resort/static routing.
Is it possible to use the same physical link but use sub-interfaces in order to keep our current setup but allow for setup of BGP and the new ARIN block over the same physical interface up to the ISP?
Has anyone transitioned this way before? Or know of any guides that might help me out in the configuration of something like this. We are still in the planing phase and I just need to know if this is a viable solution or do we get another ISP (which is going to happen anyway eventually) and migrate over external services that way.
Thank you,
Jon

Jon
Am I correct in understanding that you have a single router connecting to a single ISP for Internet connectivity? And that the ISP handles routing to you and you have static routes pointing to the ISP? And that you now have been assigned your own block of addresses?
If I have understood correctly then I will suggest to you that you may not need to use BGP as you implement the new address block. I would suggest that you could use this approach:
- configure the new address block inside your network. Ask your ISP to route to these addresses over the existing connection (the ISP should be able to establish a static route for this block in their routing logic).
- your ISP might ask you to advertise the address block to them. In that case you may need to run a dynamic routing protocol between your router and the ISP. Ask the ISP what routing protocol they support. BGP is probably one alternative but the ISP may have other routing protocols that they support for customer connections.
HTH
Rick

MIB and BGP peer (BGP4-MIB::bgpPeerRemoteAddr)

Hello,
We're using NAGIOS to monitor the networks of our customers.
We're using BGPv4 and vrf lite on many of those networks.
On every remote routers, we have multiple bgp peer sessions facing two ASR-1002F backbone routers (GRT and VRFs...).
I'd like to know if there's a way to monitor all bgp sessions, on a remote router, without having to enter the ip addresses of all neighbors....
I'm wondering whether or not I can use the "bgpPeerState" state to monitor the status of these bgp peer sessions?
Someone got an idea?
Thanks in advance,
BRGs
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mso-fareast-language:EN-US;}
xxxxx@NOC-SV-PL-SUP01:/usr/local/nagios/libexec$ snmpwalk -v 2c -c TESTRO 172.27.20.119 BGP4-MIB::bgpPeerRemoteAddr
BGP4-MIB::bgpPeerRemoteAddr.10.40.3.25 = IpAddress: 10.40.3.25
BGP4-MIB::bgpPeerRemoteAddr.10.40.3.29 = IpAddress: 10.40.3.29
BGP4-MIB::bgpPeerRemoteAddr.10.40.8.153 = IpAddress: 10.40.8.153
BGP4-MIB::bgpPeerRemoteAddr.10.40.8.157 = IpAddress: 10.40.8.157
BGP4-MIB::bgpPeerRemoteAddr.172.25.3.17 = IpAddress: 172.25.3.17
BGP4-MIB::bgpPeerRemoteAddr.172.25.3.18 = IpAddress: 172.25.3.18
nsoc-iec@NOC-SV-PL-SUP01:/usr/local/nagios/libexec$ snmpwalk -v 2c -c TESTRO 172.27.20.119 BGP4-MIB::bgpPeerState.10.40.3.25
BGP4-MIB::bgpPeerState.10.40.3.25 = INTEGER: established(6)

Hello Joseph,
Thanks for your answer.
We've been testing some scripts and it's now working!
We use the bgpPeerRemoteAddrMIB to get our ip @ and then we log any change in bgpPeerStateper ip@...
An alarm is on when we have an IDLE state....
Warning for the other BGP states
OK for established.
Regards
Katy Desrosiers

Routing query on EIGRP and OSPF

Hi,
Suppose i have 2 routers connected by using ethernet link. I have 2 internal network connected to each routers.
Now i am using OSPF routing protocol between the routers and i made adjancies only with the ethernet interface ip address ie /30 subent.
Now my query, will my internal network will get advertised by learning internally or do i want to advertise by using network command.
Again.. do i want to advertise with passive interface command or not. what is the difference in enabling ospf for all networks.
Attached a sample diagram which my setup clearly.
I want to know, what the is difference if i advertise the internal network with passive interface enabled and not.
May be the query is simple, but i am missing to understand one point and looking for the someone to explain that.
Also the sme using EIGRP, will it make any difference. As i understood the network command in IGP is same,
Regards,Gan

Gan
You have choices about how you can get OSPF and EIGRP to advertise the LAN subnets that you have configured. Let me start with the obvious point that you must have a network statement for the subnet that connects the two routers. The network statement is necessary to have the routing protocol run on those connecting interfaces.
Beyond the connecting interfaces you have a choice about how to get the routing protocol to advertise the LAN subnets. You could use network statements that match the LAN subnets. This will result in the routing protocol running on the LAN interfaces as well as the connecting interface. This is the approach that is frequently used but not the only option. You can also redistribute connected into the routing protocol. Redistribute connected will result in the routing protocol advertising the subnets but the routing protocol will not run on the LAN interfaces. The other thing to consider is that if you redistribute the subnets they will be advertised as External routes in the routing protocol.
If you do use network statements for the LAN subnets then there is the question of whether to use passive interface for the LAN subnets. When you use passive interface the routing protocol does not send any hello messages on those interfaces, will not create any neighbor relationships on those interfaces, and will not accept any routing updates from those interfaces. If there are no routers connected on those interfaces and no other devices that need to participate in the routing protocol then passive interface may be a good option to consider as it reduces the overhead processing on the interface.
HTH
Rick

EIGRP and BGP

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