From: Ronald Salomon (rsalomon@xxxxxxxxxxxxxxxx)
Date: Tue Jan 25 2000 - 15:59:54 GMT-3
Ben,
Let me preface my answer by first saying that because IGRP does not
support VLSM you will not have full connectivity within your IGRP
domain. The subnets of 129.45.0.0 are discontigous throughout the IGRP
domain. The only networks that R3 will see from R2 are /30 subnets;
reason being, R2 cannot advertise a /29 network out an interface that
support a /30 subnet. The same is true for R2. With that said:
Answer Q.1: The passive-interface command simply makes the router a
silent host (listens to routing updates but does not advertise) on
the data-link referenced. Since loopback interfaces are software only
interfaces, updates are suppressed by default -- there's no place for
the update to "physically" go :)
which makes me wonder why Cisco has that as an option for the
passive-interface sub-commands; maybe someone else can elaborate.
Answer Q.2: You will not see 129.45.80.128/29 in the IGRP domain if
the only neighbor you have is directly connected on R3/S0, for the
same reason outlined in the "preface". To see this network within IGRP
you have to change the mask to /30 for it to be advertised out to R2.
If left alone as /29 only /29 connected interfaces on ASBR(R3) will
forward the route.
Ronald
----- Original Message -----
From: Ben Rife
To: ccielab@groupstudy.com
Sent: Monday, January 24, 2000 11:17 PM
Subject: IGRP Issues
Hi Everyone,
1st Question:
I have two routers R2 and R3
R2----------R3
R2 has 3 interfaces:
Lo0: 129.45.80.72 /30
E0 : 129.45.80.144 /29
S0 : 129.45.80.4 /30
router igrp 100
net 129.45.0.0
passive-interface lo 0
R3 has 3 interfaces:
S0 : 129.45.80.4 /30
E0 : 129.45.80.48 /30
S1 : 129.45.80.128 /29
router igrp 100
net 129.45.0.0
passive-interface e0
passive-interface s1
On R3, when I "sh ip route", I see R2's loopback in my table. Why? I
thought by "passive-int lo 0", I wouldn't see it?
2nd Question:
If I run OSPF on R3's S1 interface, will I be able to redistribute
that into IGRP since it is a /29 ?
Please explain, it's been a long day and I'm not thinking straight.
Thanks,
Ben
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