Cisco BGP config

Discussion in 'Hardware' started by 0racle, Aug 25, 2010.

  1. 0racle

    0racle

    Joined:
    Aug 25, 2010
    Messages:
    1
    First off, network configs aren't really my area.

    Anyway, we are moving from one ISP to another. We have a private BGP ASN with the first and decided to keep that config, so I have to configure BGP for the new ISP. We are going to be readdressing our equipment so we received a new IP block from the new ISP. Obviously we need to advertise this block to the new ISP and filter advertisements relating to the old IP block.

    Obviously if I do nothing, both IP blocks are advertised to the new ISP. As soon as I try to filter with a route map, no routes are advertised.

    The following setup is what we have. I changed the IP blocks but the subnet masks are the same.

    OLD ISP block - 10.0.0.0/26
    OLD ISP Peer - 172.24.1.228

    NEW ISP Block - 192.168.0.0/28
    NEW ISP Peer - 192.168.0.61

    BGP Config

    router bgp XXXXX
    neighbor 172.24.1.228 remote-as YYYY
    neighbor 172.24.1.228 ebgp-multihop 10
    neighbor 192.168.0.61 remote-as ZZZZ
    neighbor 192.168.0.61 ebgp-multihop 10

    address-family ipv4
    neighbor 172.24.1.228 activate
    neighbor 192.168.0.61 activate
    neighbor 192.168.0.61 soft-reconfiguration inbound
    neighbor 192.168.0.61 route-map in_newisp in
    neighbor 192.168.0.61 route-map to_newisp out
    no auto-summary
    no synchronization
    network 10.0.0.0 mask 255.255.255.192
    network 192.168.0.240 mask 255.255.255.240
    !
    ip prefix-list newisp description Routes To NewISP
    ip prefix-list newisp seq 10 permit 192.168.0.0/28
    !
    ip prefix-list from_newisp seq 5 permit 0.0.0.0/0

    !
    route-map to_newisp permit 10
    match ip address prefix-list newisp
    !
    route-map in_newisp permit 5
    match ip address prefix-list from_newisp
    !

    How on earth do I filter to allow 192.168.0.240/28 to be advertised to 192.168.0.61 but 10.0.0.0/26 isn't.
    0racle, Aug 25, 2010
    #1
    1. Advertising

  2. 0racle

    Akilla21

    Joined:
    Nov 2, 2010
    Messages:
    14
    Location:
    Wiesbaden, Germany
    Aren't you advertising the 10.0.0.0 subnet with your network statement? If you don't want your neigbhor to receive the advertisement the simpliest to me is to remove the network statement.

    The route-maps are advanced statements but you could also set a condition based on the match. And that condition will be to deny advertisements to specific neighbors with the route-map is applied.

    I don't see any set conditions on your route-map, so it is seeing but what does BGP do with it?
    Akilla21, Nov 3, 2010
    #2
    1. Advertising

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