Cisco Systems Setting icmp unreachables limit - ASA

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Subject Author Date
Setting icmp unreachables limit - ASA Pseto 06-11-08
Posted by Pseto on June 11, 2008, 10:13 am
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How to set up icmp unreachable limit in ASA (Software Version 7.0(6))? I
tried with icmp unreachable rate-limit command, but it seems that this
command is not supported on my ASA.
The reason I want to change defaults is that I want my ASA generates such
messages a little bit faster because I believe that default value causes
some problems with specific connections.

regards


Posted by Andrey Tarasov on June 11, 2008, 12:48 pm
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Pseto wrote:
> How to set up icmp unreachable limit in ASA (Software Version 7.0(6))? I
> tried with icmp unreachable rate-limit command, but it seems that this
> command is not supported on my ASA.
> The reason I want to change defaults is that I want my ASA generates
> such messages a little bit faster because I believe that default value
> causes some problems with specific connections.

Do you mind to describe what kind of connections are those? I can think
of the only scenario where ICMP unreachables are used - path MTU
discovery. And ASA (as PIX) has sysopt command to lower MSS. If I
remember correctly it's 1300 by default.

Regards,
Andrey.

Posted by Pseto on June 12, 2008, 4:00 am
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it's Cisco VPN client behind my ASA that needs to connect to the LAN behind
Cisco 851 router with EasyVPN server on it. This 851 router is connected to
the Internet with PPPoE. I manage to establish vpn client successfully with
tens of other easy vpn servers (not connected with pppoe), but this one. On
the other side, I can establish connection with this pppoe vpn server if the
client is behind Linksys broadband router with pppoe connection... So, I
believe it has to be MTU issue. Since it's about udp connection I don't see
how mss would help.
Inspecting traffic with wireshark I noticed the following: sending ping
(with df set) packets exceeding MTU value of outside ASA interface forces
ASA to send unreachables, but it sends maybe one or two unreachable packets
per minute. Maybe vpn client connection time out interval is too short, so
it don't see unreachables and cannot perform pmtud.




Posted by Pseto on June 13, 2008, 10:33 am
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It appears that after all problem lies somewhere in my ISP network. I just
plugged my laptop instead of ASA right behind ISP router and vpn connection
still does not work?! ;)

regards


> How to set up icmp unreachable limit in ASA (Software Version 7.0(6))? I
> tried with icmp unreachable rate-limit command, but it seems that this
> command is not supported on my ASA.
> The reason I want to change defaults is that I want my ASA generates such
> messages a little bit faster because I believe that default value causes
> some problems with specific connections.
>
> regards
>


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