Two default routes

[netmaniac]

Can someone tell me what happens if in my Internet routers I have 2 default route? does it affect my traffic and if some one can give me name of the tool from which can analysze which user/users are doing download or FTP on internet link and using chunk of the B/W

Thank you

[Josef Oduwo]

The network that has the lowest administrative distance is chosen as the network for the gateway of last resort. If all the networks have the same AD then the network listed first in the routing table is chosen as the network for the gateway of last resort.

If you use both the ip default-network and ip route 0.0.0.0 0.0.0.0 commands to configure candidate default networks, and the network used by the ip default-network command is known statically, the network defined with the ip default-network command takes precedence and is chosen for the gateway of last resort.

And if the network used by the ip default-network command is derived by a routing protocol, the ip route 0.0.0.0 0.0.0.0 command, which has a lower administrative distance, takes precedence and is chosen for the gateway of last resort. If you use multiple ip route 0.0.0.0 0.0.0.0 commands to configure a default route, traffic is load-balanced over the multiple routes.

More at http://www.cisco.com/warp/public/105/default.html.

Otherwise there are several tools you could use to analyse user traffic. Check out http://www.ethereal.com, http://www.nagios.com, http://www.mtrgs.org (not sure about the URL for this one). There is also a plethora of commercial stuff out there as well, but I don't know about those :)

Josef.

PS - rate the post if it helps...

[jdilley]

Do you have 2 default routes on 2 different routers pointing to the same ISP? Or do you have 2 different default routes on one router pointing to two different ISPs. You can span a port on your LAN segment and use a freeware program called Ethereal to passively capture traffic and filter down and see who is using FTP.

[netmaniac]

I have two diffrent default route on one of the internet router the default route are pointing to two diffrent ISP.........

[kapishmohole.cisco]

If you have two default routes like

ip route 0.0.0.0 0.0.0.0 a.b.c.d

ip route 0.0.0.0 0.0.0.0 w.x.y.z

Then also your internet traffic will be load balanced on these links, by default it will be load balanced on per-destination basis.

You can start a SPAN session on router for LAN segment (you need two LAN ports on router second for destination of SPAN).

After that you can use tools like Maatec, this tool will give you per user basis bandwidth consumption, statistics for per IP and ports in use http://www.maatec.com/mtna/index.html

Kapish

[netmaniac]

I am not sure if you are right, you answer appears logical to me but , just tell me if this load balaning will happen if it is with diffrent ISP as well.....there are two diffrent ISP and two diffrent DMZ firewall for both the router...still load balancing will happen or not.??? thank you

[kapishmohole.cisco]

Load balancing will happen in this case.

Router has two default routes with same AD, and as per any switching mechanism- process switching, CEF, fast switching by default load balancing per destination is active.

If you don’t have fast packet or CEF running then also any Cisco router/any IOS version uses process switching method for all types of traffic, and load balance per destination basis.

But per destination basis load balancing does not ensure EQUAL (50 – 50%) load balancing.

Kapish