BGP with Multiple ISP not functioning

[mbbmani]

Hi,

I have 3 BGP session with 3 ISP using 3 routers.

The BGP session works but only 1 at a time.

Below are my configs

router bgp 22222
 bgp log-neighbor-changes
 neighbor YYY.YYY.YYY.YYY remote-as 123456
 !
 address-family ipv4
  bgp dampening
  network XXX.XXX.XXX.0 mask 255.255.255.252
  network XXX.XXX.XXX.16 mask 255.255.255.240
  network XXX.XXX.XXX.32 mask 255.255.255.224
  network XXX.XXX.XXX.64 mask 255.255.255.192
  network XXX.XXX.XXX.128 mask 255.255.255.128
  network XXX.XXX.XXY.0 mask 255.255.255.0
  network XXX.XXX.XXZ.0 mask 255.255.255.0
  aggregate-address XXX.XXX.XXX.0 255.255.252.0 summary-only
  neighbor YYY.YYY.YYY.YYY activate
  neighbor YYY.YYY.YYY.YYY remove-private-as
  neighbor YYY.YYY.YYY.YYY soft-reconfiguration inbound
  neighbor YYY.YYY.YYY.YYY prefix-list inbound-route-filter in
  neighbor YYY.YYY.YYY.YYY prefix-list route-advertise out
 exit-address-family
!

What could it be the problem.

Please advice.

[Muhammad Uzair]

Please remove the static route from NTT-Router also one more thing I observed that out of 3 ISP's you are doing prepanding for 1 which I cannot see in your BGP config which you shared. strange thing is you are prepanding to AS 10204 and then they are handing over to AS 38278 which is one of your ISP and have direct peering with you but not advertising your /22 block over the internet, do you have any CCIE or CCNP to maintain your AS? please make sure you are advertising the block "Network 103.100.204.5 Mask 255.255.255.252" in your BGP AS by going "router bgp (AS#)"

Kindest regards,

Uzzi

[Muhammad Uzair]

The main issue that you are facing is that R1 R2 R3 don't have complete information of each others connected networks and static routes. What is happening is that when you trace from R2 taking the source of your Gi0/1.8 interface the out traffic goes to the connected ISP and the return traffic till hop 3 also comes back through the same ISP to R2, from hop 4 onward the return path is through either ISP 1 or ISP 3 (whichever is most suitable through BGP path selection criteria) when the return traffic comes back through ISP 1 through router 1 router 1 doesn't have the route to reach the source IP of R2 interface Gi0/1.8, you can verify this by displaying "show ip route" ip address of R2 gi0/1.8 interface, R1 will have no entry for this IP address.

If the above is not true then you have to check the load balance config which might be dropping the traffic coming from R1 the source of R2 interface; due to reverse path check fail.

You can implement 3 solutions.

(1) Either run a IGP between R1 R2 R3 (most suitable for scalability ).

(2) You can redistribute connected/static routes into BGP on all R1 R2 R3 (But be careful to filter out any more specific than /24 prefix to your ISP)

(3) Use static route to define all connected networks of R1 R2 R3 to each other.

Kindest regards,

Uzzi

[Dennis Mink]

your configuration ofr AS22222 only contains one neighbour.  why is there no 3 nieghbours if you have 3 ISPs?

[paul driver]

Hello

Your config shows you only have ebgp peering and no ibgp between each rtr

as such external routes cannot be shared between each rtr and also each rtr isn’t aware of each other   

As for each rtr not able to each the internet can you confirm what interfaces you are basing your source on? - if this is the internal lan interface are you performing any NAT for this?

res

paul

[mbbmani]

Hi,

The source interface of the ping is the Internal ISP independent IP segment (public ip).

I have no NAT for this interface.

I have shortage of physical interface in this router. It is cisco 2911.

0/0 - WAN IP (connect to ISP)

0/1 - LAN IP (ISP independent IP - which is what I am working on)

0/2 - LAN IP (ISP provided IP segment)

Can I use secondary IP in int 0/1 or loopback for iBGP?

Thanks.