BGP Design question.

Brant I. Stevens branto at
Wed Jun 22 22:33:57 UTC 2011

On 6/22/11 6:27 PM, "Bret Palsson" <bret at> wrote:

>Here is my current setup in ASCII art. (Please view in a fixed width
>font.) Below the art I'll write out the setup.
>     +--------+    +--------+
>     | Peer A |    | Peer A |  <-Many carriers. Using 1 carrier
>     +---+----+    +----+---+    for this scenario.
>         |eBGP          | eBGP
>         |              |
>     +---+----+iBGP+----+---+
>     | Router +----+ Router |  <-Netiron CERs Routers.
>     +-+------+    +------+-+
>       |A   `.P    A.'    |P   <-A/P indicates Active/Passive
>       |      `.  .'      |      link.
>       |        ::        |
>     +-+------+'  `+------+-+
>     |Act. FW |    |Pas. FW |  <-Firewalls Active/Passive.
>     +--------+    +--------+
>To keep this scenario simple, I'm multihoming to one carrier.
>I have two Netiron CERs. Each have a eBGP connection to the same peer.
>The CERs have an iBGP connection to each other.
>That works all fine and dandy. Feel free to comment, however if you think
>there is a better way to do this.
>Here comes the tricky part. I have two firewalls in an Active/Passive
>setup. When one fails the other is configured exactly the same
>and picks up where the other left off. (Yes, all the sessions etc. are
>actively mirrored between the devices)
>I am using OSPFv2 between the CERs and the Firewalls. Failover works just
>fine, however when I fail an OSPF link that has the active default route,
>ingress traffic still routes fine and dandy, but egress traffic doesn't.
>Both Netiron's OSPF are setup to advertise they are the default route.
>What I'm wondering is, if OSPF is the right solution for this. How do
>others solve this problem?

You could also do an eBGP session through the firewall between the outside
routers and routers on the inside firewall, passing only the default route
to the inside routers.
>Note: Since lately ipv6 has been a hot topic, I'll state that after we
>get the BGP all figured out and working properly, ipv6 is our next
>project. :)

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