From: Baety Wayne A 30 SIG BN RS3 (cn) (BaetyWA@schofield.army.mil)
Date: Tue Jun 22 2004 - 16:47:07 GMT-3
The simplest solution is to enable OSPF on the 3550 and add the lo0 and
3550-R5 links to your OSPF routing process. But if you cannot enable OSPF
(by the lab specifically stating you may not enable OSPF on the 3550-R5
link), the next simplest solution is to enable another shared routing
protocol on the 3550-R5 link and then selectively redistributing learned
networks into the OSPF process on R5. Many alternate routing protocols have
a way of self-originating a default route on R5 to your 3550, including
OSPF, and then filtering all other routes. A routing protocol generated
default route doesn't violate the no "static default" rule. You may do the
second solution as long as the lab doesn't have verbiage about not enabling
any routing-process on the 3550-R5 link.
The third option is to rely on proxy arp on the 3550, which in most cases
leads to arp cache thrashing, is a performance hit and shouldn't be used in
a live network. By enabling proxy arp on R5 (on by default) and using a
shorter subnet mask on the 3550, the 3550 will use arp to obtain
reach-ability to the rest of the network. You can also use secondary
networks on the 3550 to make it believe other networks are local to its
R5-3550 link, in which case R5 will respond with an arp reply for each
instance. Then use PBR on R5 to reach the loopback of the 3550.
The fourth option is to disable routing on the 3550 and use ip
default-network pointing to R5. This takes care of one direction, 3550 to
the rest of the world. Then use PBR on R5, creating a route-map pointing to
destinations of lo0 to the 3550. This takes care of reach-ability to the
3550's lo0, both traffic directions satisfied. If the lab specifically
states you can not use a _default network_ (note: this is not a static
default route which is of the form ip route 0.0.0.0 x.x.x.x....) or
specifically states you can not disable routing on the 3550, then there are
other ways of getting the 3550 to view R5 in "default" ways. IRDP is one,
which requires you to disable routing on the 3550 and enabling IRDP style
Gateway Discovery Protocol. DHCP is another (requires the EasyIP feature
set). IRDP relies on the fact that you configure R5 (by enabling ip irdp)
to broadcast or multicast hello messages on the 3550-R5 link. What's neat
about IRDP is that you can configure static routes with it w/o violating
many labs static route rule w/ its proxy-advertise feature. If you enable
ip gdp irdp on the 3550 and ip irdp on R5 you can take care of both traffic
directions.
Keep in mind these labs are designed to test how fluid you are with
configuring a Cisco router. So, learn all the ways you can configure
reach-ability and you should be all set. (Ever heard of ODR?)
Regards,
WAYNE A. BAETY, Contr, 30SIG BN
MCSE+I, MCSD, MCDBA, CCNP+Voice
Resident System Support Specialist
Office: (808) 655-6761
Cell: (808) 779-3776
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ccie2be
Sent: Tuesday, June 22, 2004 5:17 AM
To: MMoniz; Group Study
Subject: Re: Routing without routing protocol
Hey Mike,
Option isn't allowed - the instructions explicitly told me to enable ip
routing on the 3550.
Re: irdp. I thought of that this morning but I thought if irdp were used, it
would have to be on the 3550. However, since there's no routing protocol
running on the link between the 3550 and R5, there wouldn't be any routing
updates to listen for.
Also, if I remember correctly, irdp only listens for rip or igrp updates and
only ospf is running on R5.
I think there's still something else I'm missing.
Thanks, I'm sure I'll find out, Tim
----- Original Message -----
From: "MMoniz" <ccie2002@tampabay.rr.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; "Group Study" <ccielab@groupstudy.com>
Sent: Tuesday, June 22, 2004 10:28 AM
Subject: RE: Routing without routing protocol
> Well I would say you have basically 2 options here.
>
> 1. Use IRDP on R5
>
> 2. Disable IP routing on the Cat and configure a default-gateway. This is
> not a static route or a static network!!
>
> Mike
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> ccie2be
> Sent: Tuesday, June 22, 2004 10:10 AM
> To: Group Study
> Subject: Routing without routing protocol
>
>
> Hi All,
>
> This one got me.
>
> 3550 has routing enabled but no routing protocols enabled.
>
> It's only path to the rest of the network is via R5. All other routers on
> the
> other side of R5 must be able to ping the 3550's loopback.
>
> I'm allowed to use one static route on R5.
>
> This is what it looks like:
>
> 3550 lo0 fa0/5 ------- e0/1 R5 ----- rest of network
>
> How do I provide reachabiltiy to the 3550's lo0 without violating lab
rules
> ie
> no default routes or default networks and
> no static routes except the one explicitly allowed here?
>
> Please tell me what I'm missing. Thanks, Tim
>
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