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Old 10-29-2005, 02:07 PM   #1
Registered: Aug 2005
Location: NY,USA
Distribution: Debian, Gentoo, Ubuntu
Posts: 103

Rep: Reputation: 15
router issue - kernel routing tables?

I have one problem on two servers that i use as routers (two houses, two completely separate networks) , so i'm 110% sure it is something in my configuration. The issue happens without the iptables rules even loaded, so I'm 99% sure it does not have to do with iptables.

when i first turn on the routers, i ping google from it and it is under 20ms... but then if i do it again a couple minutes later, itll be 100ms+ until i reset the interface connected to the internet (ifdown eth1 && ifup eth1). The ping will go back down to 20, but a couple minutes later itll be back up to 100ms again.

configuration: my LAN router running debian:
eth0: LAN
eth1: internet

current kernel routing table:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
localnet * U 0 0 0 eth0 * U 0 0 0 eth1
default ool-45796001.dy UG 0 0 0 eth1

let me know any other information you need, I am desperate to resolve this as it is causing performance issues on both networks.

and after a couple minutes on a ssh connection into the box (from over the internet) it gets really laggy and then locks up... but then a new connection can be opened, act fine, then do the same exact thing.

another issue:

i have a webserver running on on port 6080. When i request http://domain:6080 from within the same LAN as the webserver, I get connection refused. When I connect to within the LAN, it works perfectly.
When someone outside the network requests http://domain:6080, it works fine.

Again, i suspect this has to do with the kernel routing tables in my router.

edit: i think the difference in google pings may just be shifting routes chosen over the internet, for load balancing. I'm more concernde now with the laggy/frozen ssh connections and the webserver/local server access

Last edited by FliesLikeABrick; 10-29-2005 at 04:05 PM.
Old 11-02-2005, 08:11 PM   #2
Senior Member
Registered: Feb 2002
Location: Szczecin, Poland
Distribution: Gentoo, Debian
Posts: 2,458

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Using a domain in the url will always get the external number, which creates a routing problem.

Any reply from the server will come from it's internal interface and ip number and the client will drop these packets as they are from the wrong ip..

Use a local dns solution (/etc/hosts even) to supply the internal ip number for the domains on the server.

The slowing net connection could be a changing path MTU which causes packets to become fragmented, slowing the whole link down. Try disabling auto MTU discovery, or even cut the entire network down to an MTU of 1400 and see the effect it makes.
Old 11-02-2005, 08:21 PM   #3
Registered: Aug 2005
Location: NY,USA
Distribution: Debian, Gentoo, Ubuntu
Posts: 103

Original Poster
Rep: Reputation: 15
i'll look into what you said about the domain stuff.

i think the slowing down interface is because of the NIC. It is one of the first (or maybe THE first) revision of Linksys's USB1.1 10/100 adapter.

I'm gonna try just setting up the routing using the two onboard NICs and see if that clears up the bog-down issue, then later I'll see what is up with that NIC.


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