BGP question - need help !!!

Discussion in 'Cisco' started by yellow, Oct 24, 2005.

  1. yellow

    yellow Guest

    Hi,

    I'm having 2 routers conencting to separate isp, these 2 routers are
    running egp to the isp and running ibgp between them.

    ISP A (AS100) ISP B (AS200)
    | |
    | |
    rtr A (AS900) -- ibgp -- rtr B (AS900)
    *It uses ISPA ip block and receive full routes from both isps.
    Two routers are running hsrp, NO OSPF or other internal routing
    protocol is running between them.


    Rtr A

    router bgp 900
    no synchronization
    bgp log-neighbor-changes
    bgp bestpath compare-routerid
    bgp dampening
    network 10.1.1.0
    neighbor 20.6.6.7 remote-as 100
    neighbor 20.6.6.7 soft-reconfiguration inbound
    neighbor 20.6.6.7 filter-list 1 out
    neighbor 10.1.1.1 remote-as 900
    neighbor 10.1.1.1 next-hop-self

    Rtr B

    router bgp 900
    no synchronization
    bgp log-neighbor-changes
    bgp bestpath compare-routerid
    bgp dampening
    network 10.1.1.0
    neighbor 30.6.6.7 remote-as 200
    neighbor 30.6.6.7 soft-reconfiguration inbound
    neighbor 30.6.6.7 filter-list 1 out
    neighbor 10.1.1.2 remote-as 900
    neighbor 10.1.1.2 next-hop-self

    - My problem now is : when I checked rtr A routing table (sh ip bgp),
    it doesn't receive all the route from Rtr B. Some specific dest (e.g.
    12.8.1.0) only shows one best route via isp A, the route via Rtr B
    doesn't appear in routing table. Why Rtr A behaves differently ?

    - when I check routing table on Rtr B, I could see all the route
    received from Rtr A and every destination has two routing path.

    - In case ISP A failure (Rtr A is still up & running), will this route
    - 12.8.1.0. failover to Rtr B automatically ?


    - when I type sh ip bgp 12.8.1.0 on Rtr B, I could see following
    'Advertised to upadte-groups' info. :

    BGP routing table entry for 12.8.1.0/23, version 24780039
    Paths: (2 available, best #2, table Default-IP-Routing-Table)
    Advertised to update-groups:
    2

    - When I type th same on Rtr A, it shows following 'Advertised to
    non-peer group peers' :

    BGP routing table entry for 12.8.1.0/23, version 29880351
    Paths: (2 available, best #2, table Default-IP-Routing-Table)
    Advertised to non peer-group peers:

    - why Rtr A does not accept the parameter of 'updated-group'. When 2
    routers establish ibgp, they should under the same peer group. Why does
    Rtr A shows 'Advertised to updated-groups', while Rtr B shows
    'Advertised to non peer-group peers' ? Does it mean my ibgp
    configuration is incompleted ?

    Many thanks in advance :)
     
    yellow, Oct 24, 2005
    #1
    1. Advertising

  2. - My problem now is : when I checked rtr A routing table (sh ip bgp),
    it doesn't receive all the route from Rtr B. Some specific dest (e.g.
    12.8.1.0) only shows one best route via isp A, the route via Rtr B
    doesn't appear in routing table. Why Rtr A behaves differently ?

    Router B has the better path, therefore router A doesn't populate it's BGP
    or routing table with that update.

    - In case ISP A failure (Rtr A is still up & running), will this route
    - 12.8.1.0. failover to Rtr B automatically ?

    I believe it will, but I always tell my customers that the best way to
    determine this is to schedule downtime and do a failover test.




    Regards,
    Steve
    www.networking-forum.com



    "yellow" <> wrote in message
    news:...
    > Hi,
    >
    > I'm having 2 routers conencting to separate isp, these 2 routers are
    > running egp to the isp and running ibgp between them.
    >
    > ISP A (AS100) ISP B (AS200)
    > | |
    > | |
    > rtr A (AS900) -- ibgp -- rtr B (AS900)
    > *It uses ISPA ip block and receive full routes from both isps.
    > Two routers are running hsrp, NO OSPF or other internal routing
    > protocol is running between them.
    >
    >
    > Rtr A
    >
    > router bgp 900
    > no synchronization
    > bgp log-neighbor-changes
    > bgp bestpath compare-routerid
    > bgp dampening
    > network 10.1.1.0
    > neighbor 20.6.6.7 remote-as 100
    > neighbor 20.6.6.7 soft-reconfiguration inbound
    > neighbor 20.6.6.7 filter-list 1 out
    > neighbor 10.1.1.1 remote-as 900
    > neighbor 10.1.1.1 next-hop-self
    >
    > Rtr B
    >
    > router bgp 900
    > no synchronization
    > bgp log-neighbor-changes
    > bgp bestpath compare-routerid
    > bgp dampening
    > network 10.1.1.0
    > neighbor 30.6.6.7 remote-as 200
    > neighbor 30.6.6.7 soft-reconfiguration inbound
    > neighbor 30.6.6.7 filter-list 1 out
    > neighbor 10.1.1.2 remote-as 900
    > neighbor 10.1.1.2 next-hop-self
    >
    > - My problem now is : when I checked rtr A routing table (sh ip bgp),
    > it doesn't receive all the route from Rtr B. Some specific dest (e.g.
    > 12.8.1.0) only shows one best route via isp A, the route via Rtr B
    > doesn't appear in routing table. Why Rtr A behaves differently ?
    >
    > - when I check routing table on Rtr B, I could see all the route
    > received from Rtr A and every destination has two routing path.
    >
    > - In case ISP A failure (Rtr A is still up & running), will this route
    > - 12.8.1.0. failover to Rtr B automatically ?
    >
    >
    > - when I type sh ip bgp 12.8.1.0 on Rtr B, I could see following
    > 'Advertised to upadte-groups' info. :
    >
    > BGP routing table entry for 12.8.1.0/23, version 24780039
    > Paths: (2 available, best #2, table Default-IP-Routing-Table)
    > Advertised to update-groups:
    > 2
    >
    > - When I type th same on Rtr A, it shows following 'Advertised to
    > non-peer group peers' :
    >
    > BGP routing table entry for 12.8.1.0/23, version 29880351
    > Paths: (2 available, best #2, table Default-IP-Routing-Table)
    > Advertised to non peer-group peers:
    >
    > - why Rtr A does not accept the parameter of 'updated-group'. When 2
    > routers establish ibgp, they should under the same peer group. Why does
    > Rtr A shows 'Advertised to updated-groups', while Rtr B shows
    > 'Advertised to non peer-group peers' ? Does it mean my ibgp
    > configuration is incompleted ?
    >
    > Many thanks in advance :)
    >
     
    www.networking-forum.com, Oct 24, 2005
    #2
    1. Advertising

  3. In article <>,
    "yellow" <> wrote:

    > - My problem now is : when I checked rtr A routing table (sh ip bgp),
    > it doesn't receive all the route from Rtr B. Some specific dest (e.g.
    > 12.8.1.0) only shows one best route via isp A, the route via Rtr B
    > doesn't appear in routing table. Why Rtr A behaves differently ?


    In BGP, you only advertise the best route to your neighbors. Since B
    considers the route it learned from A to be better than the one it
    learned from the ISP, it doesn't advertise the ISP route back to A.

    >
    > - when I check routing table on Rtr B, I could see all the route
    > received from Rtr A and every destination has two routing path.


    The ISP A routes are all better than the ISP B routes, so Rtr A
    advertises all its routes to Rtr B.

    >
    > - In case ISP A failure (Rtr A is still up & running), will this route
    > - 12.8.1.0. failover to Rtr B automatically ?


    Yes. When the connection to ISP A goes down, Rtr A will withdraw its
    routes from its advertisements. Then Rtr B's best (and only) routes
    will be the ones it learned from ISP B, so it will advertise them to Rtr
    A.

    >
    >
    > - when I type sh ip bgp 12.8.1.0 on Rtr B, I could see following
    > 'Advertised to upadte-groups' info. :
    >
    > BGP routing table entry for 12.8.1.0/23, version 24780039
    > Paths: (2 available, best #2, table Default-IP-Routing-Table)
    > Advertised to update-groups:
    > 2
    >
    > - When I type th same on Rtr A, it shows following 'Advertised to
    > non-peer group peers' :
    >
    > BGP routing table entry for 12.8.1.0/23, version 29880351
    > Paths: (2 available, best #2, table Default-IP-Routing-Table)
    > Advertised to non peer-group peers:
    >
    > - why Rtr A does not accept the parameter of 'updated-group'. When 2
    > routers establish ibgp, they should under the same peer group. Why does
    > Rtr A shows 'Advertised to updated-groups', while Rtr B shows
    > 'Advertised to non peer-group peers' ? Does it mean my ibgp
    > configuration is incompleted ?


    I didn't see anything about peer groups in the BGP configurations you
    posted.

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
     
    Barry Margolin, Oct 25, 2005
    #3
  4. yellow

    yellow Guest

    Barry Margolin 寫é“:

    > In article <>,
    > "yellow" <> wrote:
    >
    > > - My problem now is : when I checked rtr A routing table (sh ip bgp),
    > > it doesn't receive all the route from Rtr B. Some specific dest (e.g.
    > > 12.8.1.0) only shows one best route via isp A, the route via Rtr B
    > > doesn't appear in routing table. Why Rtr A behaves differently ?

    >
    > In BGP, you only advertise the best route to your neighbors. Since B
    > considers the route it learned from A to be better than the one it
    > learned from the ISP, it doesn't advertise the ISP route back to A.
    >
    > >
    > > - when I check routing table on Rtr B, I could see all the route
    > > received from Rtr A and every destination has two routing path.

    >
    > The ISP A routes are all better than the ISP B routes, so Rtr A
    > advertises all its routes to Rtr B.
    >
    > >
    > > - In case ISP A failure (Rtr A is still up & running), will this route
    > > - 12.8.1.0. failover to Rtr B automatically ?

    >
    > Yes. When the connection to ISP A goes down, Rtr A will withdraw its
    > routes from its advertisements. Then Rtr B's best (and only) routes
    > will be the ones it learned from ISP B, so it will advertise them to Rtr
    > A.
    >
    > >
    > >
    > > - when I type sh ip bgp 12.8.1.0 on Rtr B, I could see following
    > > 'Advertised to upadte-groups' info. :
    > >
    > > BGP routing table entry for 12.8.1.0/23, version 24780039
    > > Paths: (2 available, best #2, table Default-IP-Routing-Table)
    > > Advertised to update-groups:
    > > 2
    > >
    > > - When I type th same on Rtr A, it shows following 'Advertised to
    > > non-peer group peers' :
    > >
    > > BGP routing table entry for 12.8.1.0/23, version 29880351
    > > Paths: (2 available, best #2, table Default-IP-Routing-Table)
    > > Advertised to non peer-group peers:
    > >
    > > - why Rtr A does not accept the parameter of 'updated-group'. When 2
    > > routers establish ibgp, they should under the same peer group. Why does
    > > Rtr A shows 'Advertised to updated-groups', while Rtr B shows
    > > 'Advertised to non peer-group peers' ? Does it mean my ibgp
    > > configuration is incompleted ?

    >
    > I didn't see anything about peer groups in the BGP configurations you
    > posted.
    >
    > --
    > Barry Margolin,
    > Arlington, MA
    > *** PLEASE post questions in newsgroups, not directly to me ***

    Hi, If i don't setup peer group, will it affect the failover function &
    route updates between these two routers ? If my site only has 2 Rtrs,
    do you still suggest to use peer group ?

    Thanks,
    Thanks
     
    yellow, Oct 25, 2005
    #4
  5. In article <>,
    "yellow" <> wrote:

    > Hi, If i don't setup peer group, will it affect the failover function &
    > route updates between these two routers ? If my site only has 2 Rtrs,
    > do you still suggest to use peer group ?


    Peer groups are useful when you have several neighbors that you want to
    use the same options with. You list the options in the peer group
    configuration, and then use "neighbor x.x.x.x peer-group XXXX" for each
    neighbor. If you only have two routers, there's no need for peer groups.

    P.S. Did you really need to quote *everything* just to ask this question?

    --
    Barry Margolin,
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
     
    Barry Margolin, Oct 26, 2005
    #5
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