[c-nsp] need help about network

[Vinny Abello]

Check for something like TCP Offload on the machine where you are seeing this problem. This can often interfere with things and result in incorrect TCP checksums in packet captures. Outside of that, do you have an MTU smaller than 1500 bytes anywhere you know of in the network? It could be broken PMTU discovery due to overzealous ICMP blocking somewhere or routers with unreachables disabled completely.

-Vinny

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of ann kok
> Sent: Thursday, December 04, 2008 1:23 PM
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] need help about network
> 
> Hi
> 
> I have problem to access this site eg: outsidewebsite.com
> but this machine can work other website
> 
> I also tried to use other machine in different network to access the
> same website (outsidewebsite.com). It works. but those machines are not
> acessing    outsidewebsite.com in the same network
> 
> I am sure there is no firewall and this website won't block any 80 from
> outside
> 
> 
> I get "incorret" in the tcpdump.
> 
> Do you have any idea?
> 
> 12:38:36.339248 IP (tos 0x8, ttl 64, id 54019, offset 0, flags [DF],
> proto TCP (6), length 40) 192.168.0.21.33786 > outsidewebsite.com.http:
> ., cksum 0xe114 (correct), ack 304 win 6432
> 
> 12:38:36.355895 IP (tos 0x8, ttl 64, id 54020, offset 0, flags [DF],
> proto TCP (6), length 238) 192.168.0.21.33786 >
> outsidewebsite.com.http: P, cksum 0xb071 (incorrect (-> 0xf336),
> 206:404(198) ack 304 win 6432
> 
> Thank you
> 
> 
> 
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