Quagga BGP – How to Advertise Non-Transitive Routes

bgpquagga

I have two ebgp peers connected to my quagga 1.0.20160315 router.

One of those peers (peer1) is advertising routes with flag 0x800 (Optional Non-Transitive) in the MP_REACH_NLRI path attribute.
Also the next hop is marked as Optional Non-Transitive.

My quagga router is not advertising this route to the other peer2 and I suspect this is because of the Non-Transitive flags in the path attribute.

Is their a way to override non-transitive flag in incoming routes and redistribute them to all the other peers?

Thanks in advance for the help.
Regards

Update
I got it working by using a route map and re-writing the bgp next hop. Original route was not advertised because of Non Transitive flags.

router bgp 64496  
bgp router-id 192.168.56.1  
network 192.1.1.0/24  
 !  
 redistribute connected  
 neighbor 192.168.20.201 remote-as 64496  
 neighbor 192.168.20.201 route-reflector-client  
 neighbor 192.168.20.201 update-source 192.168.20.1  
 neighbor 192.168.20.201 soft-reconfiguration inbound  
redistribute connected  
 neighbor 192.168.56.202 remote-as 64498  
 neighbor 192.168.56.202 update-source 192.168.56.1  
 neighbor 192.168.56.202 soft-reconfiguration inbound  
 neighbor 192.168.56.202 route-map set-nexthop out  
!  
route-map set-nexthop permit 10  
 set ip next-hop 192.168.56.1  
 set metric 200  
 set local-preference 5  
!

Best Answer

No, you cannot change the flag. Attribute MP_REACH_NLRI is defined to be Optional Non-Transitive in RFC4760. What kind of routes you are trying to advertise?

Update Neighbor to 192.168.20.201 in same AS(64496) is iBGP, not eBGP. You should be able to fix it easily by changing local AS or neighbor AS.

The reason why it wasn't working before you set nexthop is that Quagga router received routes from 192.168.20.201 but their nexthop cannot be used. You can use neighbor <peer> next-hop-self to fix it instead of route-map.

Also if you want to run eBGP for all routers, you don't need to configure neighbor <peer> route-reflector-client which is for iBGP.

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By the data that you give us, this one is an interesting part. Unless you had change the neighbors for your safety, and put the conf here, i think you need to explaind why your iBGP neighbor has the same IP address of your UPDATE SOURCE? This one is like if your iBGP share your same host.

neighbor 1.1.1.1 description "R101 BGP interconnect"
neighbor 1.1.1.1 update-source 1.1.1.1
neighbor 1.1.1.1 next-hop-self
neighbor 1.1.1.1 send-community both
neighbor 1.1.1.1 soft-reconfiguration inbound

neighbor 1.1.1.2 description "R102 BGP interconnect"
neighbor 1.1.1.2 update-source 1.1.1.2
neighbor 1.1.1.2 next-hop-self
neighbor 1.1.1.2 send-community both
neighbor 1.1.1.2 soft-reconfiguration inbound

Routing – Quagga not announcing external routes over ibgp session

The update-source isn't used for eBGP unless you use eBGP multihop (which you aren't), and it's unnecessary for your iBGP since you are not sourcing from a different interface from the one which you are using to connect the neighbors. You should remove those lines.

You don't seem to be using communities, so you can lose the lines with send-community both. Normally you would have consistent communities on prefixes within your AS, and you would only use that when you need to send your communities to a different AS.

Your iBGP routers should be sharing their BGP routing tables already, so the soft-reconfiguration inbound shouldn't be used within your AS, but it is often used between ASes.

I'm not sure why you are prepending the same number of ASes to both the external routers. Normally you use prepending to have the external AS to prefer one of your routers over the other; you would prepend on one external link but not the other. The way you are doing doesn't seem like it accomplishes anything.

Since you want to advertise aggregate prefixes, use the aggregate-address command. This will advertise the summary routes, and based on what you commented, I think this is your goal. The aggregate addresses will be advertised as long as there is at least one route within the summary in your routing table. the summary-only means that it will not advertise the individual routes that are within the aggregate address.

I think your BGP configurations should look something like:

R101:

router bgp 1
 no synchronization
 bgp router-id 0.0.0.1
 bgp log-neighbor-changes
! network 1.0.0.0
! network 2.0.0.0
 aggregate-address 1.1.1.0 255.255.255.0 summary-only
 aggregate-address 2.2.2.0 255.255.255.0 summary-only
 neighbor 4.4.4.1 remote-as 2
 neighbor 4.4.4.1 description "R101 uplink"
 neighbor 4.4.4.1 update-source 4.4.4.2
 neighbor 4.4.4.1 route-map R1-MAP out
 neighbor 4.4.4.1 soft-reconfiguration inbound
 neighbor 1.1.1.2 remote-as 1
 neighbor 1.1.1.2 description "R101 BGP interconnect"
 neighbor 1.1.1.2 next-hop-self
 maximum-paths 2
 no auto-summary
!

R102:

router bgp 1
 no synchronization
 bgp router-id 0.0.0.2
 bgp log-neighbor-changes
! network 1.0.0.0
! network 2.0.0.0
 aggregate-address 1.1.1.0 255.255.255.0 summary-only
 aggregate-address 2.2.2.0 255.255.255.0 summary-only
 neighbor 3.3.3.1 remote-as 2
 neighbor 3.3.3.1 description "R102 uplink"
 neighbor 3.3.3.1 update-source 3.3.3.2
 neighbor 3.3.3.1 route-map R102-MAP out
 neighbor 3.3.3.1 soft-reconfiguration inbound
 neighbor 1.1.1.1 remote-as 1
 neighbor 1.1.1.1 description "R102 BGP interconnect"
 neighbor 1.1.1.1 next-hop-self
 no auto-summary
!

Best Answer

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