From: Jon Carmichael (jonc@xxxxxxxxxxx)
Date: Wed May 23 2001 - 18:59:43 GMT-3
If my memory is working, OSPF hellos use PROTOCOL 89. I'm not certain
that's the number tho. You could try something like...
dialer-list 1 protocol ip list 101
access-list 101 deny 89 any any
access-list 101 permit ICMP any any echo
access-list 101 permit ICMP any any echo-reply.
That would make OSPF NOT interesting, and make pings interesting.
Actually, --just using an access list of any kind in the above manner lets
you control what brings the link up in a very granular way. A usual safe
bet would be to..
access-list 101 permit TCP any any
without specifying a port number. You KNOW the OSPF hello (keepalivees)
are not going to be carried in TCP.
JONC
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Devinder Singh
Sent: Wednesday, May 23, 2001 11:01 AM
To: 'ccielab@groupstudy.com'
Subject: OSPF Virtual Link / BGP/DLSW over ISDN
Hello all
I was trying to configure OSPF virtual Link over ISDN. But with this
configuration, link comes up every time. Seems like there are some
additional OSPF packets (may be keepalive) which flow through, bringing
isdn circuit up. Is there any way to make it work??
Basically what I am trying to do is this- Normally R1 connects to R2 which
has an interface in area 0 directly and there is no virtual link
configuration required there. When this connection to Backbone router fails,
BRI should come up which connects to another router R3. ISDN link is
configured in area 3 so a virtual link needs to be configured for OSPF to
work over ISDN along with Demand Circuit.
Without any virtual link configuration, OSPF Demand circuit works perfectly
well i.e. Hello's are suppressed and neighbor relationship are formed.
Area 0 \ Area 2
R2------------------------------R3
| /
| /
| /
Area 0 | / ISDN
Primary Link / Area 3
| /
| /
R1
With Virtual Link configuration on, I gave "debug dialer packet " and in
its output, I see periodic packets exchange between R1 and R3 with source
and destination IP of BRI interface which brings the link up. Is it HELLO
Packet as over virtual link, it should be a specific IP instead of Multicast
address (I am not sure), But then it should get suppressed. Any clues???
I also tried configuring BGP over ISDN and had similar issues. What is the
way if BGP neighbor relationship need to be formed over ISDN link. Anything
to do with timers or is it a special dialer-list?? (I saw a posting once on
this list but couldn't find on archives)
On similar lines, what would be required to configure DLSW peers over
ISDN?? Any special precautions. I haven't tried that yet
Thanks in advance.
Dev
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