Brian,
Thanks for the example - hitting the loopbacks on REMOTE routers is easy to
understand (as is loopback interfaces for BGP connections and OSPF Router
IDs). However, I've seen traffic being routed to an IP address on the same
subnet as the router's loopback interface is on. Eg.
E0 > R1 > Loop 0 > R1 > S0 > R2 > E0 > IP destination
The actual destination IP address might be a subnet on some other remote
router but the traffic is first directed to an IP address on the same subnet
as the router's own loopback address. I believe its done to avoid some sort
of traffic from hitting NAT on the way out, but having an access-list
definition for NAT traffic should already take care of this.
Take a look at the initial route-map configuration I gave - traffic from E0
bound for network 192.168.2.0/24 (not a destination on the router's own
connected interfaces) is set for next-hop IP address of 192.168.255.2 (the
router's loopback IP address is 192.168.255.1 with a /24 mask).
Regards,
Adrian
"Brian" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> On Fri, 28 Jul 2000, Adrian Chew wrote:
>
> > I've seen this in some configurations where traffic is sent via a
route-map
> > to an IP address that is on the same subnet as a router's loopback
> > interface.
> >
> > Eg.
> >
> > interface ethernet 0
> > ip address 192.168.1.1 255.255.255.0
> > ip policy route-map abc
> >
> > interface loopback 0
> > ip address 192.168.255.1 255.255.255.0
> >
> > access-list 100 permit ip 192.168.1.0 0.0.0.255 192.168.2.0 0.0.0.255
> >
> > route-map abc permit 10
> > match ip address 100
> > set ip next-hop 192.168.255.2
> >
> > Could anyone explain how having traffic routed via a loopback interface
> > might help in certain situations?
>
> load balacing for one.........
>
> For example:
>
> R1
> ip cef
>
> int loopback 0
> ip address 10.1.1.1 255.255.255.0
>
> int ethernet 0
> ip address 192.168.2.1 255.255.255.0
>
> int serial 0
> ip address 192.168.1.1 255.255.255.252
> ip load-sharing per-packet
>
> int serial 1
> ip address 192.168.1.5 255.255.255.252
> ip load-sharing per-packet
>
> ip route 10.1.2.1 255.255.255.0 192.168.1.2
> ip route 10.1.2.1 255.255.255.0 192.168.1.6
> ip route 0.0.0.0 0.0.0.0 10.1.2.1
>
> R2
> ip cef
>
> int loopback 0
> ip address 10.1.2.1 255.255.255.0
>
> int serial 0
> ip address 192.168.1.2 255.255.255.252
> ip load-sharing per-packet
>
> int serial 1
> ip address 192.168.1.6 255.255.255.252
> ip load-sharing per-packet
>
> ip route 10.1.1.1 255.255.255.0 192.168.1.1
> ip route 10.1.1.1 255.255.255.0 192.168.1.5
> ip route 192.168.2.0 255.255.255.0 10.1.1.1
>
> You could save yourself some configuring and whatnot by using an IGP to
> get the dual routes injected instead of declaring them statically here,
> but I did static here to illustrate
>
> Brian
>
> >
> > Thanks.
> >
> > Regards,
> > Adrian
> >
> >
> > ___________________________________
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> >
>
> -----------------------------------------------
> Brian Feeny, CCNA, CCDA [EMAIL PROTECTED]
> Network Administrator
> ShreveNet Inc. (ASN 11881)
>
> ___________________________________
> UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html
> FAQ, list archives, and subscription info: http://www.groupstudy.com
> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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