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Re: OT: Weird routing issues



I would need to see the traceroutes...
both directions would be the best - you might be able to find a looking glass in the
network where ebay is hosted.

You may also have PMTU problems...

I can't remember if ebay drop ICMPs.

$ ping www.ebay.com
PING hp-core.ebay.com (66.135.208.90): 56 data bytes
^C
--- hp-core.ebay.com ping statistics ---
30 packets transmitted, 0 packets received, 100% packet loss

Looks like they do! Although I DO hope that someone allows PMTU messages through....


You may want to check the config on your cisco for dropping ICMPs as well.

Easiest way to test PMTU is with pings... do an extended ping from the cisco, and keep increasing the packet size - ensure that the Dont Fragment bit is set. If it stops working before 1500 bytes for the whole
packet, you then know where the problem is.




Andrew


On Feb 21, 2005, at 8:21 PM, Micah Stetson wrote:

I apologize for asking this question here, but I'm not sure where
better to ask it.  If people would like to respond via private mail or
direct me to a better group to ask, I'd appreciate it.

I work for a small ISP that uses Debian servers (here the on-topicness
ends).  We've recently gotten an ADSL connection from SBC which we've
connected to a Cisco 3640 router: the ADSL bridge is connected to an
ethernet port on the router on which we run a pppoe client.  The pppoe
interface is set as the default gateway on the router and we're using
a subnet of the IP addresses we've been assigned from SBC on another
of the router's ethernet interfaces.  If I hook up a laptop (or other
equipment) to that ethernet and configure it with an IP in that subnet
with the router as its default gateway, everything works just as I
would expect it to ... mostly.  The problem is that a few web sites
are horribly slow (notably www.ebay.com, but we've found a couple of
others).

If, from the laptop, I telnet to www.ebay.com on port 80, type 'GET
/', and hit enter, then Ebay's front page comes back, but
packet-by-packet, with about 15 seconds between packets.  If I do the
same thing from the router itself, I get nothing back, and after a few
seconds, www.ebay.com closes the connection.  If, however, I hit enter
twice after typing 'GET /' on the router, I get the whole page
immediately.  Other web sites come back immediately on both the laptop
and the router.  Traceroutes and tcptraceroutes to www.ebay.com and
other web servers don't seem to differ significantly.  But if I switch
to a different Internet connection (a T1 from Sprint) on a different
router, all the problems go away.  Also, we have a few ADSL customers
connected through the 3640 router (their PPPoE sessions terminate
there), they use the SBC DSL line to get to the Internet, and have no
problems at all.

I've gone over the configuration of the router a number of times, and
have yet to see anything out of order.  I'm nearly at my wits' end,
and I'd appreciate any suggestions I get.

Sorry, again, for the off-topic post,

Micah


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