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#909 - 07/09/03 11:39 AM Pinging Default Gateway
Anonymous
Unregistered


Comcast is saying that packet losses we are experiencing are not their fault. I'd like to run a test that includes the default gateway (192.168.98.1). Is there a way to add that hop in 2.4.1?

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#910 - 07/09/03 12:00 PM Re: Pinging Default Gateway
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
In general, if running a traceroute out to an external address doesn't show 192.168.98.1, then you won't be able to coerce Ping Plotter into reporting on that specific router in the same instance that you're tracing to the external address.

Now, let's have a look at possible problems based on the information you gave me here (which is a bit light, but I can probably point out some ideas for you).

First off, if you really want to trace 192.168.98.1, then you can set up an instance of Ping Plotter tracing to that address - and another instance tracing to another address. This will give you the packet loss results you're after. In a lot of cases, tracing to your default gateway isn't a reliable way to troubleshoot, though - as many, many cable modems won't respond to ICMP echo requests on their default gateways.

What you probably want to do is to set up a trace to a very close Comcast address (like the comcast internal SMPT or POP server, news server, or some similar customer facing, but hosted-by-Comcast address). If you get poor results tracing to this, then that's a smoking gun that there's a problem - as everything you're using for network there will be owned by Comcast.

If you don't have problems with an mail/pop/news type .comcast.com address, then you'll want to trace out of their network to a reliable destination (ie: tucows.com / yahoo.com / or similar) and see where the times start to decay. If it's at a border between comcast and another provider (ie: Cable & Wireless, AT&T, etc), then it still may be Comcast's fault - as the border might be undersized - or there may be some similar problem with the connection between Comcast and the border.

If you're getting packet loss at hop 1 (or hop 2 if hop 1 doesn't respond) all the time - to all destinations, then the problem is possibly with your physical cable modem line (ie: something between your computer and the comcast headend in their local office).

There are a lot of possibilities. If you want to post (or email to [email]support@pingplotter.com)[/email] a picture of what you're seeing (with a bunch of samples collected - 20 at a minimum, 500 would be better), then we can have a look at it and offer advice.

- Pete

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#911 - 07/09/03 01:14 PM Re: Pinging Default Gateway [Re: Pete Ness]
Anonymous
Unregistered


Thanks for the excellent suggestions. A pp2 file has been sent to you by email.

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#912 - 07/10/03 06:52 PM Re: Pinging Default Gateway
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
(This is an edited version of the message sent to support, along with an screenshot that has all location specific information removed. All location specific information has been replaced by (source) and (destination). For those interested, note that the two locations in question are both on the east coast of the US, so physical distance is not a contributor to this problem).

Pete:

I posted the question about pinging the router gateway. The (destination) office has Comcast. They have a Linksys BEFSR41 router connected to a brand new RCA modem connected to Comcast. For the last two weeks, they have constant lost their VPN connection to the server in (source). The IP address for (destination) is (destination). The IP address for the (source) office (with a Cisco router) is (source). After much testing, I do NOT believe that the problem is in (source). Other offices are able to connect without a problem.

At Comcast's insistence, we replaced a Watchguard SOHO with the Linksys. No improvement. I've pinged the Linksys as a separate process as you suggested and got a 0ms reply (is that no reply?) Since I cannot interpret these results adequately, I have no idea where the problem is.

I've purchased multiple copies of PingPlotter for myself and others as I am quite impressed with it.


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#913 - 07/10/03 06:56 PM Re: Pinging Default Gateway [Re: Pete Ness]
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
(this is the slightly edited response by me).

Hi, Mike.

You're going to have a relatively hard time troubleshooting this from the (source) side of things. There are a couple of possibilities - one is that it is a problem in (destination). The other is that there is a problem in (source), or someplace between (source) and (destination).

If the problem is with (destination), then that should be readily apparent if you run Ping Plotter in (destination) and have a look at the results there. You should see packet loss near hop 1 or hop 2 there - and that packet loss (and latency spike) will carry on through the rest of the route. Ideally, you'd trace from (destination) to (source), but if you're constantly using a VPN, this might be impossible because of the way your VPN software routes. You *should* be able to trace to the IP address of your VPN server in (source), though - which is just as good as any other address in your physical building (even if it's a different computer than you normally use Ping Plotter from).

If the problem is in (source), then this is because of asynchronous routing - which is a bit harder to diagnose, but if you have control of both ends of the connection (which it sounds like you do), then you'll be able to diagnose.

We had a good discussion on asynchronous routing here:

http://www.pingplotter.com/forums/showflat.php?Board=Support&Number=731

(note that the link to ispworld no longer works, and I've not yet found a new source for this information).

If you run a Ping Plotter trace from (destination) to (source) and send me that data, then I'll be happy to help you diagnose the location of the problem. Note that we will need to have at least one period of problems to do a good diagnosis. Ideally, you'd be running Ping Plotter from both directions so we'd get a good set of data to know the entire route - from you (in (source)), to (destination), and then back again.

The *return* route can definitely cause you pains from only one of your remote sites and not others - because your ISP might be peering with different ISPs and just one of those is behaving poorly.

Also, note that you won't be able to trace from (source) to the gateway in (destination) - as the gateway IP address you gave me isn't internet routable.

- Pete

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#914 - 07/13/03 08:39 AM Re: Pinging Default Gateway [Re: Pete Ness]
Anonymous
Unregistered


Here's what we have done to isolate the source of the problem, although I'm not sure that we have corrected it. I had a colleage ping the ISP's default gateway (the one that is handed out by DHCP to the Linksys router) from the outside while I pinged it from the inside. The problem is definitely between Comcast's default gateway and the client machines.

I swapped the two 8-port switches for new ones as it appears that the problem is on the internal network. It will be next week before I can do more troubleshooting, but PingPlotter has been a great tool for this effort. Thanks for the suggestions.


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