Sorry, knew I should have waited before I had more caffeine before
emailing :)
Ok, from the top. On Cisco boxes, the 'network' statement under the
routing protocol does 2 things.
1) Allows neighbor establishment with neighbors in that netblock
2) Allows that routing protocol to inject routes it knows about
(external to the routing process), into the topology table for that
routing process.
So let's say you have under your 'router ospf 1' process
'network 150.20.0.0'
That will mean that the router will establish adjacencies with neighbors
in the 150.20.x.x range, and will inject by default any
locally-connected interfaces it has, as long as they're contained within
the 150.20.x.x range.
So if the router has 4 interfaces.
150.20.1.1/24
150.20.200.1/30
150.20.255.255/32
151.20.1.1/24
The routing process will establish adjacencies with neighbors on the
first 3 interfaces, and will inject those first 3 interface networks
into the topology table for the routing process.
It will not however inject the last one because it's not contained
within the 150.20.0.0/16 netblock you have as a network statement.
Ken Matlock
Network Analyst
Exempla Healthcare
(303) 467-4671
[email protected]
-----Original Message-----
From: Alef [mailto:[email protected]]
Sent: Friday, June 24, 2011 8:24 AM
To: Matlock, Kenneth L
Cc: [email protected]
Subject: Re: [OSL | CCIE_RS] vol1 27.2 why are the links in OSPF not
advertisedas in EIGRP
So you're saying when we have network
a /27 and network b /26 and network c /24
it would be ok to just advertise in the 32 host routes /p2p links and
the networks would still be known without explicitly advertising them in
(As in say ospf?)
On Jun 24, 2011, at 1:37 PM, Matlock, Kenneth L wrote:
> Maybe I misinterpreted the question, but het, that's never stopped me
before :)
>
> The 'network' statement on the routing protocol doesn't necessarily
specify the EXACT netblock to announce.
>
> The 'network' statement merely gives you what range of netblocks to
announce, or establish neighbor adjacencies on. So a 'network
150.50.25.2' statement says to establish neighbor adjacencies with
anything 150.50.0.0 range (150.x.x.x is in the class 'B' range, so by
default has a /16 netmask unless you tell it different), and announce
any connected interfaces that are in the 150.50.0.0/16 range.
>
> Personally in production I purposely restrict down the network
statements to the smallest possible, but that's only so I know it's a
100% conscious decision that I'm injecting a route into the production
route tables :)
>
> Make sense?
> Ken
>
> ________________________________
>
> From: [email protected] on behalf of Alef
> Sent: Fri 6/24/2011 4:36 AM
> To: [email protected] IE
> Subject: [OSL | CCIE_RS] vol1 27.2 why are the links in OSPF not
advertisedas in EIGRP
>
>
>
> In this task, the the assignment seems the same (apart from the
configure the network statements to include the network mask) but the
link is advertised as:
>
> network 150.50.25.2
>
> and not as 150.50.25.0 0.0.0.3 or 0.0.0.1
>
> in 27.1 eigrp does advertise as a /30, 0.0.0.3
>
> is it not best practice to always advertise the networks into any
routing protocol properly ?
>
> Alef
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