Subject: Route set with REJECT flag in the IP route table - regd

From: james <[email-masked]>
Date: Wed, 03 Jun 1998 09:26:13 -0700

Hello !

The following has details of a RIP implementation. I need clarification
for the problem mentioned. Thanks in advance.

have a nice day,
sudarshan
 
Salient features of RIP daemon implemented :
----------------
I have a RIP daemon which sends and receives RIPv1 packets. It also
receives
RIPv2 packet and uses only the subnet mask of the route entries. All
other
RIPv2 spcific information are ignored. The daemon does not send RIPv2
packets.

The RIPv2 routes are installed in IP route table with the subnet mask
received as part of the RIP packet. The host routes are not installed in
IP route table but interface network information is installed in IP
route
table. 

Problem :
-------
Assume a router has 2 interfaces configured with 164.164.10.100, 
164.164.20.100 with all netmask being 255.255.255.0.
Assume that the same router has another interface with IP address 
165.165.10.100 and netmask 255.255.0.0 configured to reach router R.
RIP daemon should not advertise 164.164.10.0 and 164.164.20.0 to 
router R (as per RIPv1 RFC). But it will advertise route information
for 164.164.10.0 to the interface with IP address 164.164.20.100 and
vice-versa.
The router has a default route to router R. This default route is
selected if
no other route is available.
Doubts :
1. What route information is advertised to router R ?
2. If e.g. 164.164.0.0 is advertised then how my 
router (with RIP daemon running is the only routing protocol running)
will ensure that a packet to 164.164.30.100 cannot be forwarded ?

---

From: Acee Lindem <[email-masked]>
Date: Wed, 03 Jun 1998 10:18:50 -0400

> Salient features of RIP daemon implemented :

Since router R is using RIPv1 you can advertise the  class B (164.164/16) 
or no route at all. 

> will ensure that a packet to 164.164.30.100 cannot be forwarded ?

You could install 164.164/16 as a reject route (i.e., a route which causes 
packets to be dropped and ICMP host unreachables to be sent). 

-- 
Acee