Re: Weird path MTU autodiscovery problem in 4.5-RELEASE

2002-02-01 Thread Crist J. Clark 

On Fri, Feb 01, 2002 at 02:53:26PM +0200, Alexey Luckyanchikov wrote:
> Hello,
> 
> I have such network topology:
> 
> ++++++
> | Server |< MTU 1500 >| Router |< MTU 1476 >| Client |
> ++++++

[snip]

> 14:06:48.682558 router > server: icmp: client unreachable - need to frag (mtu 1476) 
>for server.7 > client.1371: [|tcp] (DF) (ttl 61, id 25428, len 1500) (ttl 253, id 
>2491, len 56)
> ^^
> Router say to server that he must to decrease packet size

Is "router" the same IP address that "server" has as the route to
"client?" That is, there aren't any aliases on "router's" interface
with "server" making problems?
-- 
Crist J. Clark | [EMAIL PROTECTED]
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Re: Weird path MTU autodiscovery problem in 4.5-RELEASE

2002-02-01 Thread Louis A. Mamakos 


Is the server filtering out ICMP traffic with ipfw or something?

> Alexey Luckyanchikov wrote:
> 
> 
> > 14:06:48.477578 server.7 > client.1371: . 1437:2897(1460) ack 10001 win 65535 (DF) 
>(ttl 64, id 25428, len 1500)
> > ^^^
> > Server send packet with size 1500 bytes
> > 
> > 14:06:48.682558 router > server: icmp: client unreachable - need to frag (mtu 
>1476) for server.7 > client.1371: [|tcp] (DF) (ttl 61, id 25428, len 1500) (ttl 253, 
>id 2491, len 56)
> > ^^
> > Router say to server that he must to decrease packet size
> > 
> > 14:07:04.477857 server.7 > client.1371: . 1437:2897(1460) ack 10001 win 65535 (DF) 
>(ttl 64, id 52781, len 1500)
> > ^
> > But server ignore this information and still send 1500 bytes packets
> 
> 
> What's the result of 'sysctl net.inet.tcp.path_mtu_discovery'  ??  Not that
> I can imagine, at the moment, what would set it to 0
> 
> 
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