Reachability to Backbone Routes

From: Antonio Soares (amsoares@netcabo.pt)
Date: Fri Jul 06 2007 - 16:39:33 ART

Hello group,

I've been thinking about this for a while and i don't see an easy solution
to it.

Suppose that R1 is receiving some RIP routes from a Backbone router:

+++++++++++++++++++++++++++++
R1#sh ip route rip
R 172.16.0.0/16 [120/4] via 200.200.200.254, 00:00:27, Ethernet1/0
R 10.0.0.0/8 [120/4] via 200.200.200.254, 00:00:27, Ethernet1/0
R 192.168.1.0/24 [120/4] via 200.200.200.254, 00:00:27, Ethernet1/0
R1#
+++++++++++++++++++++++++++++

And then you are asked to have full reachability to these routes from all
your routers including R1 of course.

But the Backbone has some restrictions and you are not told which is the
host portion of each route been announced:

+++++++++++++++++++++++++++++
BB1:

!
interface Ethernet0
 ip address 200.200.200.254 255.255.255.0
 ip access-group 101 in
 no ip unreachables
 no ip proxy-arp
 no cdp enable
!
access-list 101 deny icmp any 0.0.0.255 255.255.255.0
access-list 101 deny icmp any 0.0.255.255 255.255.0.0
access-list 101 deny icmp any 0.255.255.255 255.0.0.0
access-list 101 permit ip any any
!
+++++++++++++++++++++++++++++

What would you do to verify reachibility ? I thought, well with a class C is
somewhat easy but time consuming. I will do a tcl script in order to ping
all the 254 possible hosts:

Foreach ip {

ping 192.168.1.1
ping 192.168.1.2
ping 192.168.1.3
(...)
ping 192.168.1.254
} {ping $ip}

But for a class B i would need 65534 lines !!! And for a class A 16777214
lines !!!!

So the question that matters: in the real lab are we given the necessary
information to verify reachability to the backbone routes ?

Thanks,
Antonio

This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:40 ART