[wplug] Dual Ethernet Ports - One routing table

[Weber, Lawrence A]

Thanks, I considered this but there a couple of problems.  First the
network never goes down for messages from the local subnet, only drops
messages from the gateway.  Second, there will be ~100 of these devices
per subnet.

________________________________

From: wplug-bounces+lawrence.weber=ansaldo-sts.us at wplug.org
[mailto:wplug-bounces+lawrence.weber=ansaldo-sts.us at wplug.org] On Behalf
Of Andrew Fisk
Sent: Tuesday, August 25, 2009 2:15 PM
To: General user list
Subject: Re: [wplug] Dual Ethernet Ports - One routing table


how about a cron job that fires off a ping every couple of minutes,
while not elegant, it's simple and will keep the network connection
alive. 




Andy
Spitfire Computer Services
Suite 19
2301 Duss Ave.
Ambridge, PA 15003
Phone (412) 749-0162
andy at spitcomp.com
www.spitcomp.com






On Aug 25, 2009, at Tuesday, August 25, 20092:03 PM, Weber, Lawrence A
wrote:


	I have the need to interface a Linux system to two separate
subnets.  I have run into a problem when one of the ports goes down due
to either being disconnected for a minute or due to no network traffic
for approximately 3 minutes.  When the port goes down it routes the
down-port's output to localhost.  When a valid message is then received
from a gateway, the system looks into the routing table and gets
confused because it finds two default gateways (one for each subnet).
The confusion occurs even though the default gateways are assigned to
individual interfaces (eth0 - eth1).  If it picks the wrong default
gateway, it cannot reach the gateway, so it assumes that the network is
still down and sends the response to itself.  There must be a timer
involved here too because after 4 to 5 minutes the interface
re-establishes itself and works fine.  As long as there is regular
traffic through the gateway the interface never goes down.
	 
	I have heard that there can be multiple routing tables, one for
each port and that a priority routing database is used to assign tables
to ports.  Has anyone had to implement multiple routing tables?  Does
the database need to know the subnet address for every message received
through its gateway?    
	 
	I really want to keep the configuration of this system as simple
as possible, as people who know less about networking than I do (if that
is possible) will have to set up the port parameters.  Ports will have
fixed address, no DHCP.
	 
	 
	L. A. Weber
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