From: Balogh, Jim (jim.balogh@gwl.com)
Date: Fri Dec 02 2005 - 21:13:18 GMT-3
Good link:
http://www.cisco.com/en/US/customer/tech/tk365/technologies_tech_note091
86a0080093f0a.shtml
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Chris Lewis
Sent: Friday, December 02, 2005 3:59 PM
To: swm@emanon.com; 'Schulz, Dave'; nobody@groupstudy.com; 'Anthony
Sequeira'; 'Eddie Parra'
Cc: 'Paul Borghese'; 'Mike Ollington'; 'Ed Lui'; ccielab@groupstudy.com
Subject: RE: Preventing an EIGRP/OSPF Neighbor Forming
Scott, I think the error in what you demonstrate below is expecting a
neighbor to form when you have issued the passive interface command,
that will never happen for eigrp. I stand by waht I said :) you do not
need multicast packets for a neighbor to form with EIGRP. Where I think
several people seem to be misunderstanding this is expecting passive
interface to turn off multicast for EIGRP. passive interface does turn
off multicast packets, but it also disallows unicast packets.
This is the configuration and output I am referring to
R1-------R2 connected over a serial link
R1 is configured thus
router eigrp 1
network 172.16.31.1 0.0.0.0
neighbor 172.16.31.2 Serial3/0
auto-summary
R2 is configured thus
router eigrp 1
network 172.16.31.2 0.0.0.0
neighbor 172.16.31.1 Serial1/0
auto-summary
With this setup, no multicast packets are sent by either router, the
output of debug ip packet shows the following
22:53:36.959: IP: s=172.16.31.1 (local), d=172.16.31.2 (Serial3/0),
len 60, sending
22:53:40.283: IP: s=172.16.31.2 (Serial3/0), d=172.16.31.1 (Serial3/0),
len 60, rcvd 3
22:53:41.467: IP: s=172.16.31.1 (local), d=172.16.31.2 (Serial3/0), len
60, sending
22:53:45.143: IP: s=172.16.31.2 (Serial3/0), d=172.16.31.1 (Serial3/0),
len 60, rcvd 3
22:53:46.435: IP: s=172.16.31.1 (local), d=172.16.31.2 (Serial3/0), len
60, sending
22:53:49.719: IP: s=172.16.31.2 (Serial3/0), d=172.16.31.1 (Serial3/0),
len 60, rcvd 3
22:53:51.067: IP: s=172.16.31.1 (local), d=172.16.31.2 (Serial3/0), len
60, sending
2 22:53:54.375: P: s=172.16.31.2 (Serial3/0), d=172.16.31.1 (Serial3/0),
len 60, rcvd 3
22:53:56.059: IP: s=172.16.31.1 (local), d=172.16.31.2 (Serial3/0), len
60, sending
22:53:59.355: IP: s=172.16.31.2 (Serial3/0), d=172.16.31.1 (Serial3/0),
len 60, rcvd 3
22:54:00.887: IP: s=172.16.31.1 (local), d=172.16.31.2 (Serial3/0), len
60, sending
22:54:04.303: IP: s=172.16.31.2 (Serial3/0), d=172.16.31.1 (Serial3/0),
len 60, rcvd 3
The neighbors stay stable as shown below:
Router1#sho ip eigrp nei
IP-EIGRP neighbors for process 1
H Address Interface Hold Uptime SRTT RTO Q
Seq
(sec) (ms) Cnt
Num
0 172.16.31.2 Se3/0 11 00:06:57 112 672 0
1
Router1#
Scott Morris <swm@emanon.com> wrote:
I'll beg to differ on this one. There are a few Cisco docs about it
"not working as you may think". In RIP you would be correct about
exchanging routes ONLY as unicast. In EIGRP, the multicast hellos must
be present though.
Lab output:
Emanon-R5(config)#router eigrp 100
Emanon-R5(config-router)#network 113.13.13.0
Emanon-R5(config-router)#network 172.17.155.0
44w6d: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 113.13.13.106
(Ethernet0/0) is up: new adjacency
Emanon-R5(config-router)#neighbor 113.13.13.106 ethernet0/0
Emanon-R5(config-router)#
44w6d: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 113.13.13.106
(Ethernet0/0) is down: Remote peer static/dynamic
Emanon-R5(config-router)#
44w6d: destroy peer: 113.13.13.106
Emanon-R5(config-router)#
44w6d: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 113.13.13.106
(Ethernet0/0) is up: new adjacency
Emanon-R5(config-router)#pass e0/0
Emanon-R5(config-router)#
44w6d: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 113.13.13.106
(Ethernet0/0) is down: interface passive Emanon-R5(config-router)#
44w6d: destroy peer: 113.13.13.106
Emanon-R5(config-router)#
Emanon-R5(config-router)#
Emanon-R5(config-router)#(it's been 10 minutes)
Emanon-R5(config-router)#do sh ip ei n
IP-EIGRP neighbors for process 100
Emanon-R5(config-router)#(it's been 10 more minutes)
Emanon-R5(config-router)#do sh ip prot
Routing Protocol is "eigrp 100"
Outgoing update filter list for all interfaces is not set Incoming
update filter list for all interfaces is not set Default networks
flagged in outgoing updates Default networks accepted from incoming
updates EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 EIGRP maximum
hopcount 100 EIGRP maximum metric variance 1
Redistributing: eigrp 100
EIGRP NSF-aware route hold timer is 240s Automatic network summarization
is in effect Automatic address summarization:
113.0.0.0/8 for Serial0/1
Summarizing with metric 281600
Maximum path: 4
Routing for Networks:
113.0.0.0
172.17.0.0
Passive Interface(s):
Ethernet0/0
Routing Information Sources:
Gateway Distance Last Update
(this router) 90 00:20:12
113.13.13.106 90 00:19:52
Distance: internal 90 external 170
Emanon-R5(config-router)#
Emanon-R5(config-router)# (After 20 minutes and a can of Mountain Dew, I
still have no neighbors with the multicast disabled)
We could probably do some obnoxious NAT stuff though to convert into a
full unicast, but that would likely be evil. I believe someone else had
posted a config down this path.
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Chris Lewis
Sent: Friday, December 02, 2005 9:37 AM
To: Schulz, Dave; nobody@groupstudy.com; Anthony Sequeira; Eddie Parra
Cc: Paul Borghese; Mike Ollington; Ed Lui; ccielab@groupstudy.com
Subject: RE: Preventing an EIGRP/OSPF Neighbor Forming
You do not need to have multicast hellos for an EIGRP neighbor
relationship to form. The restriction is that if one neighbor is using
unicast, the other must too.
Chris
"Schulz, Dave" wrote:
I thought that you needed to have multicast hellos present in order for
the neighbor relationship to form...even if you configure unicast via
the neighbor command. Is this not the case? Do I have this wrong?
Dave
-----Original Message-----
From: nobody@groupstudy.com
To: Anthony Sequeira; Eddie Parra
Cc: Chris Lewis; Paul Borghese; Mike Ollington; Ed Lui;
ccielab@groupstudy.com
Sent: 12/1/2005 8:47 PM
Subject: Re: Preventing an EIGRP/OSPF Neighbor Forming
Basically if you do not use passive-interface, two routers can form a
relationship if they are BOTH configured with neighbor statements.
The behavior is EIGRP is different to things like RIP. EIGRP cannot
(currently in released versions) form a neighbor relationship if one
neighbor sends multicast and the other sends unicast.
When you configure a neighbor addresses, the interface that the unicast
hellos go through stop sending multicast hellos.
This can be fixed in newer releases and you may see one eigrp speaker
sending multicast neighbor up to an eigrp speaker sending unicast in the
future.
Chris
Anthony Sequeira wrote:
Apparently at one point in IOS with EIGRP - you could use
passive-interface in conjunction with the neighbor command in order to
only establish adjacencies with a certain system. Here is the
documentation excerpt from 12.0 on the subject:
<<routing information. When used in combination with the
passive-interface router configuration command, routing information can
be exchanged between a subset of routers and access servers on a LAN.
router eigrp 109
network 192.168.0.0
passive-interface ethernet 1
neighbor 192.168.20.4 >>>>>
As of 12.2.16 IOS this changed dramatically! Here is the new
documentation
(12.3) and configuration example:
<<<<neighbors or peers. With most routing protocols, the
passive-interface command restricts outgoing advertisements only.
However, when used with the Enhanced Interior Gateway Routing Protocol
(EIGRP), the use of the passive-interface command suppresses the
exchange of hello messages between two routers, which results in the
loss of their neighbor relationship. This behavior stops not only
routing updates from being advertised, but it also suppresses incoming
routing updates.
In the following example, EIGRP permits the sending of routing updates
to specific neighbors. One copy of the routing update is generated per
neighbor.
router eigrp 109
network 192.168.0.0
neighbor 192.168.20.4>>>>>>>
So Eddie - looks like you have a great point - we can still use the
neighbor command - it just cannot be combined with passive-interface any
more. Can someone lab this up and ensure it works? I do not have access
to a broadcast topology right now where I could try the neighbor command
alone without passive-interface.
I am assumming this feature causes EIGRP to unicast hellos only to a
certain neighbor and RESTRICTS the neighboring with anyone else.....I
would sure love to try it.......
On 12/1/05, Eddie Parra wrote: Anthony,
Is the neighbor command useless in this scenario? If you have 4 routers
on an Ethernet segment and you only want to form a neighbor relationship
with one, unicast neighbors is a viable option since multicast hellos
will then be ignored from other neighbors. Depending on how the
objective in the lab is worded, this might be a viable option.
-Eddie
On 11/30/05, Anthony Sequeira wrote:
> Chris - you are correct - I was sloppy in my post - SO SORRY - the
> distribute-list with the gateway option would prevent the reception of
> routes and does not effect the adjacency.
>
> BUT - I want to reiterate that as of 12.2.16 - the NEIGHBOR command
appears
> totally useless with EIGRP, I have confirmed this on equipment.
>
>
> On 11/30/05, Chris Lewis wrote:
> >
> > Dear All:
> >
> > This has been an interesting thread, however I've seen quite a few
> > responses that I cannot replicate on routers.
> >
> > For example in eigrp the distribute-list gateway configuration only
> > affects routes received, not the forming of neighbors. Also I have
just
> > labbed up an ethernet segment with 5 routers on it, left the OSPF
network
> > type as broadcast and the interface level command ip ospf
database-filter
> > all out worked fine on the router I applied it on, all other routers
formed
> > an adjacency on it, however after this command was applied, the
other
> > routers no longer had routes in their routing table to the loopbacks
the
> > router was originally advertising.
> >
> > If the original question was to exclude just one neighbor from
forming
> > adjacency on a multi access network for either OSPF or EIGRP and not
using
> > interface ACLs, the best suggestion I've seen is to use a service
policy on
> > the interface that relates to a class map identifying the neighbor
and the
> > action in the policy-map is drop.
> >
> > If you want to stop routes from the specific neighbor, the
distribute list
> > option makes sense.
> >
> > Chris
> >
> >
> > Paul Borghese
wrote:
> > Mike,
> >
> > If the requirement is to prevent the neighbor relationship, the
command
> > "neighbor database-filter all out" does not meet that requirement.
The
> > routers will still form a neighbor relationship. Plus it only works
on
> > ospf
> > network type Point-to-Multipoint.
> >
> > Take care,
> >
> > Paul Borghese
> >
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> > Mike
> > Ollington
> > Sent: Wednesday, November 30, 2005 10:57 AM
> > To: Ed Lui
> > Cc: Paul Borghese; ccielab@groupstudy.com
> > Subject: RE: Preventing an EIGRP/OSPF Neighbor Forming
> >
> > Ed,
> >
> > That would be changing for it the whole area thus affecting all the
> > neighbors.
> >
> > Ronald's `neighbor ip-address database-filter all out' command would
> > work fine for OSPF. Thanks Ronald.
> >
> > Cheers,
> > Mike
> >
> > -----Original Message-----
> > From: Ed Lui [mailto:edwlui@gmail.com]
> > Sent: 30 November 2005 15:52
> > To: Mike Ollington
> > Cc: Paul Borghese; ccielab@groupstudy.com
> > Subject: Re: Preventing an EIGRP/OSPF Neighbor Forming
> >
> > Mike,
> >
> > Are you allowed to use OSPF authentication ?
> >
> > Ed Lui
> >
> >
> >
> > On 11/30/05, Mike Ollington wrote:
> > > Paul,
> > >
> > > Changing those values would break all neighbours on an interface,
> > > anything to kill just the one?
> > >
> > > For example:
> > >
> > > 172.16.1.1
> > > 172.16.1.2
> > > 172.16.1.3 <- I temporarily want to prevent this neighbour.
> > > 172.16.1.4
> > >
> > > Thanks,
> > > Mike
> > >
> > > -----Original Message-----
> > > From: Paul Borghese [mailto: pborghese@groupstudy.com]
> > > Sent: 30 November 2005 15:10
> > > To: Mike Ollington
> > > Cc: ccielab@groupstudy.com
> > > Subject: Re: Preventing an EIGRP/OSPF Neighbor Forming
> > >
> > > In OSPF a neighbor relationship will not be formed if any of the
> > > following
> > > mismatch:
> > >
> > > hello/dead interval
> > > area id
> > > stub flag
> > > authentication
> > > subnet mask
> > > mtu
> > >
> > > So for example, if you change the hello interval on one side, the
> > > neighbor will not form. You can see this by doing a "debug ip ospf
> > > adj".
> > >
> > > For EIGRP, you can try changing the K values or Autonomous System
> > > number.
> > > EIGRP will for a relationship even if the hello values do not
match.
> > >
> > > Take care,
> > >
> > > Paul Borghese
> > >
> > > > Hello,
> > > >
> > > >
> > > >
> > > > Hypothetical - you have an interface with many EIGRP/OSPF
> > neighbours.
> > > > You want to prevent one; you don't want to use an interface
access
> > > list.
> > > >
> > > >
> > > >
> > > > In BGP there is the neighbour shutdown command, PIM has a
neighbour
> > > > list. Any thing similar for OSPF or EIGRP?
> > > >
> > > >
> > > >
> > > > Thanks,
> > > >
> > > > Mike
> > > >
> > >
> > >
> > >
> > >
> > >
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