[CentOS] Re: Network routes

[Scott Silva]

on 1/29/2008 2:53 PM Jason Pyeron spake the following:

-----Original Message-----

From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ross S. W. Walker

Sent: Tuesday, January 29, 2008 17:38
To: CentOS mailing list
Subject: RE: [CentOS] Network routes

Jason Pyeron wrote:

I am unable to ping NE.TW.RKB.IP1 from an outside network. Other machines which do not have access or routes for NET.WOR.KA.0 respond

just fine.

How do I get it to respond on both NET.WOR.KA.0 and NE.TW.RKB.0 given all default traffic should go through NET.WOR.KA.1 unless it is in reply to

traffic from NE.TW.RKB.1 or there is an outage.

[EMAIL PROTECTED] ~]# route -n
Kernel IP routing table

Iface


[EMAIL PROTECTED] ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:17:31:0F:04:AE

eth0:pn   Link encap:Ethernet  HWaddr 00:17:31:0F:04:AE

eth1      Link encap:Ethernet  HWaddr 00:01:03:E9:42:D0

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0

Destination Gateway Genmask Flags Metric Ref Use NET.WOR.KA.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1 192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 NE.TW.RKB.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1 0.0.0.0 NET.WOR.KA.1 0.0.0.0 UG 0 0 0 eth1 0.0.0.0 NE.TW.RKB.1 0.0.0.0 UG 20 0 0 eth0 inet addr:NE.TW.RKB.IP1 Bcast:NE.TW.RKB.255 Mask:255.255.255.0 inet addr:192.168.1.20 Bcast:192.168.1.255 Mask:255.255.255.0 inet addr:NET.WOR.KA.IP2 Bcast:NET.WOR.KA.255 Mask:255.255.255.0

You can have only 1 default route.

You can use RIP or some other routing protocol to
advertise defualt routes to the host from the
gateways based upon route availability or weight,
or you can deploy reverse NAT'ing on the gateways
so external IPs will be masqueraded as the
internal IP of the gateway and thus be routed to
the appropriate gateway based on which IP they
arrived on.

-Ross

But I have 2 physical network cards, on 2 different networks. Should they
not both have default routes?

You would think so, but it will confuse the system so bad that traffic won't know where to go. The default route is the route that packets need to take to leave your network to enter the outside world. Every thing under your control should have static routes of some kind, or a routing daemon.

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