as I suggested in my private note, there are two things to consider.
thing 1 is how routes are put into routing tables.
thing 2 is how forwarding decisions are made.
forget the static route for a minute. suppose you had a router that was
simultaneously running EIGRP and OSPF, or OSPF and RIPv2, or EIGRP and
IS-IS. never mind the specifics, but if the router learns about a router
10.50.0.0/16 via one of the protocols, and 10.48.0.0/12 from the other, what
happens, in terms of what is placed into the routing table?
one must separate the routing table from the processes that place routes
into routing tables.
in the case you state, yes indeed the router "believes" there are two
networks out there. same as it would if you were to place two static
routes - 10.50.1.1/32 and 10.50.0.0/16 Perhaps we should say "destinations"
in order to be a bit more clear?
In the case you present, the two networks are 10.48.0.0/12, which includes
10.48.0.1 through 10.63.255.254, and the 10.50.0.0/16, which includes
10.50.0.1 through 10.50.255.254
if a packet arrives at the router interface, and the destination address is
10.50.x.y, then so long as the routing table is intact, the forwarding
choice will be the /16 network. If the 10.50.0.0/16 route has been flushed,
due to a failure, then that route will have been removed from the routing
table, leaving the /12 net as the choice.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Thomas N.
Sent: Monday, September 10, 2001 10:20 PM
To: [EMAIL PROTECTED]
Subject: Re: Question on routing [7:19083]
Hi All,
First, let me sorry for the inaccurate information in the puzzle. The
static IP address 10.48.0.0 is with 12 bits subnet mask (255.240.0.0, NOT
255.224.0.0). I didn't have my subnet calculator last time. So, the scope
of IP address for 10.48.0.0/255.240.0.0 will include 10.48.0.0 to
10.63.255.255.
Well, for more specific information, I am setting up a lab in which routes
are learning dynamically with EIGRP while having a static routing pointing
for a dummy VPN boxes for redundancy. These VPN boxes only do static
mapping for routes. If the primary link between the two hub sites (learning
through EIGRP) got killed, the first hub site is supposed to route its
spokes and its subnets to reach the other hub and other spokes with static
routes. However, instead of putting a bundle of static routes, I decided to
use summaried routes (10.48.0.0/255.240.0.0) to cover. Thing is not that
simple. The router might think 10.48.0.0/12 and 10.50.0.0/16 as two
separate networks. If following the "more specific rule", the 10.50.0.0
network should act as the primary even it has administrative distance of 90.
So the 10.48.0.0/12 should be ignored even it has an administrative distance
of 1. In this case, I don't even need the floating static route (make a
static route with admin. distance greater than 90), in order to make the
static route as the secondary route for backup. Should my analyze correct?
I might setup the lab and see what the routers will act. However, I would
like to test my theory and analyzing... Please give me your thought!
Thanks!
Thomas N.
""David Goddard"" wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Thomas,
>
> This question has a lot of strange inaccuracies in it, but here we go...
>
> 1. The routing path chosen will always use the "longest match rule", in
> other words between 10.50.0.0/16 and 10.32.0.0/12 the route chosen will be
> the 10.50.0.0/16.
>
> 2. Your mask is bad for the static route... if you want routes 10.32.0.0
to
> 10.63.0.0 to be included, the static route would read:
>
> ip route 10.32.0.0 255.224.0.0 serial 1
>
> 3. Enabling eigrp requires the command ROUTER EIGRP 200, not just EIGRP
200
>
> 4. When you add the network statements
> network 172.16.1.0
> network 172.16.2.0
> to your EIGRP process, it will come out simply as
> network 172.16.0.0
> and enable the EIGRP process on both Serial 0 and Serial 1 of both
routers.
> So although you may think that you didn't put in the network statement on
> router A for 172.16.2.0, it will still enable EIGRP on Serial 1. So when
> Serial 0 goes down, routing will still continue over Serial 1.
>
> Try testing your configs out in a lab and you'll see pretty quickly what I
> mean.
>
> Dave
Message Posted at:
http://www.groupstudy.com/form/read.php?f=7&i=19380&t=19083
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