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<FONT face=Tahoma size=2><B>From:</B> centos-bounces@centos.org
[mailto:centos-bounces@centos.org] <B>On Behalf Of </B>Ross S. W.
Walker<BR><B>Sent:</B> Tuesday, January 29, 2008 18:22<BR><B>To:</B>
centos@centos.org<BR><B>Subject:</B> Re: [CentOS] Re: Network
routes<BR></FONT><BR></DIV>
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<P><FONT size=2>Sorry for the top post.<BR><BR>The default route is the route
applied when no other route matches the destination IP. From that how would
you figure out which default route to pick, only if the routes were weighted
could you pick between two.<BR><BR>If you had two routes with equal weight and
the traffic went round robin between them then the originating host will
discard half the returning traffic because it's not coming from the same ip it
sent it to.<BR><BR>No your best bet is probably to do reverse NAT'ing as it is
simple to setup and you don't have to worry about default routes and weight.
Traffic initiates on 1 gateway and sticks with it for the duration of the
session. You can use BGP on the gateways outside interface to load balance or
fail-over the default gateway or use round-robin DNS, MX records for mail,
etc.<BR><BR>-Ross<BR><BR><SPAN class=541232501-30012008><FONT
face="Courier New"> </FONT></SPAN></FONT></P></BLOCKQUOTE>
<P><FONT size=2><SPAN class=541232501-30012008>Okay, they were weighted primay
at 0 and it worked. Secondary at 20, it would never be chosen as a default. But
how does a reply get out to the net on the same route it came in
on?</SPAN></FONT></P>
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<P><FONT size=2><SPAN class=541232501-30012008> </SPAN><BR>----- Original
Message -----<BR>From: centos-bounces@centos.org
<centos-bounces@centos.org><BR>To: centos@centos.org
<centos@centos.org><BR>Sent: Tue Jan 29 18:03:13 2008<BR>Subject:
[CentOS] Re: Network routes<BR><BR>on 1/29/2008 2:53 PM Jason Pyeron spake the
following:<BR>> <BR>><BR>>> -----Original
Message-----<BR>>> From: centos-bounces@centos.org<BR>>>
[</FONT><A href="mailto:centos-bounces@centos.org"><FONT
size=2>mailto:centos-bounces@centos.org</FONT></A><FONT size=2>] On Behalf Of
Ross S. W. Walker<BR>>> Sent: Tuesday, January 29, 2008
17:38<BR>>> To: CentOS mailing list<BR>>> Subject: RE: [CentOS]
Network routes<BR>>><BR>>> Jason Pyeron wrote:<BR>>>> I
am unable to ping NE.TW.RKB.IP1 from an outside network.<BR>>>> Other
machines<BR>>>> which do not have access or routes for NET.WOR.KA.0
respond<BR>>> just fine.<BR>>>> How do I get it to respond on
both NET.WOR.KA.0 and<BR>>>> NE.TW.RKB.0 given all<BR>>>>
default traffic should go through NET.WOR.KA.1 unless it
is<BR>>>> in reply to<BR>>>> traffic from NE.TW.RKB.1 or
there is an outage.<BR>>>><BR>>>> [root@host20 ~]# route
-n<BR>>>> Kernel IP routing table<BR>>>>
Destination
Gateway
Genmask Flags
Metric<BR>>>> Ref Use<BR>>>>
Iface<BR>>>> NET.WOR.KA.0
0.0.0.0
255.255.255.0 U
0 <BR>>>>
0 0 eth1<BR>>>>
192.168.1.0
0.0.0.0
255.255.255.0 U
0 <BR>>>>
0 0 eth0<BR>>>>
NE.TW.RKB.0
0.0.0.0
255.255.255.0 U
0 <BR>>>>
0 0 eth0<BR>>>>
169.254.0.0
0.0.0.0
255.255.0.0 U
0 <BR>>>>
0 0 eth1<BR>>>>
0.0.0.0
NET.WOR.KA.1
0.0.0.0 UG
0 <BR>>>>
0 0 eth1<BR>>>>
0.0.0.0
NE.TW.RKB.1
0.0.0.0 UG
20 <BR>>>>
0 0
eth0<BR>>>><BR>>>> [root@host20 ~]# ifconfig<BR>>>>
eth0 Link encap:Ethernet HWaddr
00:17:31:0F:04:AE<BR>>>>
inet addr:NE.TW.RKB.IP1 Bcast:NE.TW.RKB.255 <BR>>>>
Mask:255.255.255.0<BR>>>> eth0:pn Link
encap:Ethernet HWaddr
00:17:31:0F:04:AE<BR>>>>
inet addr:192.168.1.20 Bcast:192.168.1.255 <BR>>>>
Mask:255.255.255.0<BR>>>> eth1 Link
encap:Ethernet HWaddr
00:01:03:E9:42:D0<BR>>>>
inet addr:NET.WOR.KA.IP2 Bcast:NET.WOR.KA.255 <BR>>>>
Mask:255.255.255.0<BR>>>>
lo Link encap:Local
Loopback<BR>>>>
inet addr:127.0.0.1 Mask:255.0.0.0<BR>>>><BR>>> You can
have only 1 default route.<BR>>><BR>>> You can use RIP or some
other routing protocol to<BR>>> advertise defualt routes to the host
from the<BR>>> gateways based upon route availability or
weight,<BR>>> or you can deploy reverse NAT'ing on the
gateways<BR>>> so external IPs will be masqueraded as the<BR>>>
internal IP of the gateway and thus be routed to<BR>>> the appropriate
gateway based on which IP they<BR>>> arrived on.<BR>>><BR>>>
-Ross<BR>>><BR>><BR>> But I have 2 physical network cards, on 2
different networks. Should they<BR>> not both have default
routes?<BR>><BR>You would think so, but it will confuse the system so bad
that traffic won't<BR>know where to go. The default route is the route that
packets need to take to<BR>leave your network to enter the outside world.
Every thing under your control<BR>should have static routes of some kind, or a
routing daemon.<BR><SPAN class=541232501-30012008><FONT
face="Courier New"> </FONT></SPAN></FONT></P></BLOCKQUOTE><FONT
size=2><SPAN class=541232501-30012008>
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-<BR>- Jason
Pyeron
PD Inc. </FONT><A href="http://www.pdinc.us/"><FONT face="Courier New"
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Consultant
10 West 24th Street #100 -<BR>- +1 (443) 269-1555
x333
Baltimore, Maryland 21218
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