From: Rick (rick@iptool.net)
Date: Thu Jan 12 2006 - 13:00:29 GMT-3
Most TCP applications/connections work this way. The port for the return
traffic will mostly be random and will be above 1024. Most of the apps
have a range they will choose for the random part, however that isn't
always the case and varies by different vendors.
You will notice the same thing with BGP, this is a snippet from a neighbor
session:
Peer: 1.1.1.1+179 AS 1 Local: 2.2.2.2+1634 AS 2
This will let you know that Peer 1.1.1.1 initiated the connection using
port 179 and 2.2.2.2 responded on port 1634.
> I am working with some reflexive ACLs. Everything is working fine,
> but.....doing a telnet from router through to another....I noticed that
> the return path was going to port 11002, rather than the expected port
> 23. I could not find any documentation on this. Does anyone have any
> information on this, or, at least point me to the information. Thanks
> in advance!
>
> R1#sh ip access
> Extended IP access list TCPIN
> 10 permit ospf any any (8 matches)
> 20 permit icmp any any (20 matches)
> 30 permit tcp any any eq telnet reflect TELNET (31 matches)
> Extended IP access list TCPOUT
> 10 permit ospf any any (1 match)
> 20 evaluate TELNET
> Reflexive IP access list TELNET
> permit tcp host 172.16.1.4 eq telnet host 192.168.1.3 eq 11002 (52
> matches) (time left 293)
>
> Dave
>
> Dave Schulz,
> Email: dschulz@dpsciences.com <mailto:dschulz@dpsciences.com >
>
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