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Bronze

Help with BGP and route-map

Hello,

I'm having an issue I was hoping someone could help me with...

My setup is as such:

Primary location has internet connection and should be used by all remotes.Primary location connected to WAN via 30mb PVC

WAN is MPLS VPN with BPG routing

Primary location advertises a default route via "network 0.0.0.0" command, not default-originate.

Disaster recovery location also has internet, but should only be used in the event the internet at primary is unavailable. DR location also on WAN via 30MB circuit.

18 other branch locations on MPLS WAN

What I'm trying to do:

I would like to advertise a default route from the DR location and make it less desirable then the default route from the primary location. To accomplish this, i've used a prefix-list to identify the default route, then  used that prefix-list in a route-map which tweaks the AS-PATH for the route.

It actually works well... there is a 2nd default route in the PE router with a higher AS-PATH. I tied the default route advertised from the Primary location to a track-object, so if the internet connection is unavailable (IP SLA pings next hop past our internet router), the default route is removed and the other route is inserted into the routing table pointing everything to the DR location for its default route.

Problem is, all the other routes from the DR location are no longer advertised, only the default route.Can someone please tell me what I'm missing? I guess I could tweak the prefix-list to match all routes (0.0.0.0/0 le 32), but I really only want to influence the default route. any thoughts? Thanks in advance!

Here's my config for the DR location:

router bgp 64519
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
redistribute connected
redistribute static
neighbor <ISP PEER> remote-as <ISPASN>
neighbor <ISP PEER> allowas-in
neighbor <ISP PEER> route-map AS-PREPEND out
no auto-summary

ip route 0.0.0.0 0.0.0.0 192.168.246.1

ip prefix-list default-route seq 5 permit 0.0.0.0/0
route-map AS-PREPEND permit 10
match ip address prefix-list default-route
set as-path prepend 64519 64519

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Help with BGP and route-map

Hello Rtjensen4,

to advertise the specific static routes you need an empty second block in your route map:

route-map AS-PREPEND permit 10
match ip address prefix-list  default-route
set as-path prepend 64519 64519

>>route-map AS-PREPEND permit 20
! other matches here if needed

the route-map acts as a route filter what is not permitted is not advertised to peer.

An implicit deny any exists.

An empty last block can be used to allow specific routes it is equivalent to a permit any

Hope to help

Giuseppe

3 REPLIES
Hall of Fame Super Silver

Re: Help with BGP and route-map

Hello Rtjensen4,

to advertise the specific static routes you need an empty second block in your route map:

route-map AS-PREPEND permit 10
match ip address prefix-list  default-route
set as-path prepend 64519 64519

>>route-map AS-PREPEND permit 20
! other matches here if needed

the route-map acts as a route filter what is not permitted is not advertised to peer.

An implicit deny any exists.

An empty last block can be used to allow specific routes it is equivalent to a permit any

Hope to help

Giuseppe

Bronze

Re: Help with BGP and route-map

That did it! THANK YOU!

Just curious, can you explain why I'd need the blank statement?

I've got this all labbed out in GNS3 right now, even created a simulated "provider" network with VPNv4 routing / VRF to get it as accurate as possible. Everything seems to be updating as expected. Time to schedule its install in the production network

Hall of Fame Super Silver

Re: Help with BGP and route-map

Hello,

>> ust curious, can you explain why I'd need the blank statement?

as I have written without that line you have only one route map block that matches only with 0.0.0.0/0.

Being the route-map invoked in a neigh x.x.x.x route-map route-map out it acts a filter and so there it does not allow additional prefixes.

the last empty block without a match or set statement acts as a permit any and allows to advertise the other IP prefixes.

in other cases like when using a route-map for PBR you don't need to provide an empty block because PBR fall backs to default destination routing

Hope to help

Giuseppe

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