[Cialug] nslookup works but ping cannot resolve

[Paul Gray]

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Nathan Stien wrote:
> On Feb 8, 2008 12:32 PM, Paul Gray <gray at cs.uni.edu> wrote:
>> I heard the suggestion, but not a confirmation, that /etc/hosts should
>> be sanity checked.
> 
> It's a fresh install of ubuntu 7.10.  /etc/hosts contains the
> definition of localhost and the standard IPv6 symbols.
> 

Then, the course of diagnostics that I would suggest:

# apt-get install tcpdump strace

bring up four terminals, and issue, respectively:

A) # tcpdump -x -s0 2>&1 | tee /tmp/tcpdump.out

B) # strace -f ping host_that_I_cannot_get_to 2>&1 | tee /tmp/strace.out

C) # iptables -L
   # iptables -t nat -L
   # route -n
   # arp -n

D) (Open on the remote host)
   # tcpdump icmp

Search the /tmp files for the root of the problem; look for icmp
echo-requests and echo-reply's.  In the end, the above should give you a
dead-on way of diagnosing the root of the problem...or at the very least
something to dump to folks out-of-band to resolve the issue.

Hope that helps.

- -PG

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