[c-nsp] Re: Source address on BGP peering set up

[Michael K. Smith]

Hello:

Am I missing something, or why couldn't you just set up two separate
neighbor statements for the two IP addresses?

Neighbor 10.0.0.1 remote-as 65000
Neighbor 192.168.0.1 remote-as 65000

Mike

On 1/17/05 3:59 PM, "Piltrafilla" <piltrafilla at gmail.com> wrote:

> Hi Brian,
> 
> If I correctly understood your explanation, you mean that I should
> replace primary IP address on peering interface, then configuring the
> old IP address on a loopback and finally setting up static routes to
> neighbors to peering interface. Isn't on that way?
> 
> For keeping ARP going on with neighbors, in case they do not have the
> same config as you, I suppose that proxy-arp should be configured. And
> I do not really like that option.
> 
> Thanks for your reply, :)
> 
> On Mon, 17 Jan 2005 10:39:04 -0600, Brian Feeny <signal at shreve.net> wrote:
>> 
>> I can understand that you are doing a migration from one network to
>> another.
>> However, there are probably easier ways of doing this.  Migrate the
>> network, and then
>> later migrate the BGP neighbors, in other words, leave them numbered
>> out of legacy space
>> until the last thing.
>> 
>> or
>> 
>> Use a loopback address on the Cisco, number that out of the new IP
>> space, or just some other
>> IP space, and use that as the update-source.
>> 
>> Brian
>> 
>> On Jan 17, 2005, at 10:27 AM, Piltrafilla wrote:
>> 
>>> Hi people,
>>> 
>>> First of all, thank you for all your replies, I'm sorry for the delay
>>> in my answer.
>>> 
>>> With your feedback I have tried a BGP peering on my home lab between a
>>> Cisco and OpenBSD bgpd:
>>> 
>>> Cisco
>>>   primary 10.0.0.1
>>>   secondary 192.168.0.1
>>> OpenBSD
>>>  primary 10.0.0.2
>>>  secondary 192.168.0.2
>>> 
>>> On OpenBSD bgpd configuration I have set up local-address for peer
>>> 10.0.0.1:
>>> 
>>>    neighbor 10.0.0.1
>>>    {
>>>        local-address           10.0.0.2
>>>        remote-as                65500
>>>    }
>>> 
>>> After configuration on both sides, I did a clear ip bgp 192.168.0.2 on
>>> the Cisco side to force reestablishing the peering as a client
>>> (ephemeral to 179). That's the tcpdump on the OpenBSD side:
>>> 
>>> 10.0.0.1.15357 > 192.168.0.2.179: S 2018010072:2018010072(0) win 16384
>>> 10.0.0.1.15357 > 192.168.0.2.179: S 2018010072:2018010072(0) win 16384
>>> 
>>> Although Cisco router has a connected secondary IP to peer
>>> 192.168.0.2, Cisco tries to set up the peering with the primary
>>> address.
>>> 
>>> A few seconds later, OpenBSD successfully establishes peering with the
>>> Cisco box as a client (ephemeral to 179) because of the possibility of
>>> configuring local-address:
>>> 
>>> 192.168.0.2.46380 > 192.168.0.1.179: S 957503115:957503115(0) win 65535
>>> 192.168.0.1.179 > 192.168.0.2.46380: S 949964186:949964186(0) ack
>>> 957503116 win 16384
>>> 192.168.0.2.46380 > 192.168.0.1.179: . ack 1 win 65535
>>> 192.168.0.2.46380 > 192.168.0.1.179: P 1:40(39) ack 1 win 65535 : BGP
>>> [|BGP OPEN] (DF) [tos 0xc0]
>>> 
>>> I know that for many of you, this config could seem in someway really
>>> stupid. That config was thought for a temporary peer migration not for
>>> a definitive config.
>>> 
>>> Any comments on the results?
>>> 
>>> Take Care,
>>> 
>>> -- Carlos
>>> 
>>> On Fri, 14 Jan 2005 15:34:32 +0000 (GMT), Stephen J. Wilcox
>>> <steve at telecomplete.co.uk> wrote:
>>>> I thought I'd chip in as everyone else has had a go at this..
>>>> 
>>>> On Fri, 14 Jan 2005, Piltrafilla wrote:
>>>> 
>>>>> Anyone knows how BGP on a Cisco router choose source IP address for
>>>>> peering
>>>>> establishment if no "update-source" command is applied to neighbor?
>>>>> Is it only
>>>>> the primary IP address on the closest interface to neighbor?
>>>> 
>>>> update-source will use the primary address, if no update source is
>>>> applied it
>>>> will use the ip on the outgoing interface
>>>> 
>>>>> For instance, let's say that you would like to set up a peering
>>>>> using a
>>>>> secondary IP address to between two directly-connected neighbors. Is
>>>>> it
>>>>> setting up loopbacks, static /32 routes and update-source on the
>>>>> neighbors'
>>>>> config the only way to do it?
>>>> 
>>>> no you can just config it like any other ebgp directly connected peer
>>>> 
>>>>> On bgpd of OpenBSD you could set up a "local-address" parameter per
>>>>> neighbor or group that sets up source IP address used for that
>>>>> peering. I haven't found any similar parameter on cisco bgp
>>>>> neighbors'
>>>>> config.
>>>> 
>>>> it doesnt have it
>>>> 
>>>> Steve
>>>>