Hi all, Please forgive the simplistic nature of the query.. Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another part of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP. Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link - I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's. Any help would be greatly appreciated. Rolo ! _________________________________________________________________ Stay in touch with absent friends - get MSN Messenger http://www.msn.co.uk/messenger
Rolo Tomassi wrote:
Hi all,
Please forgive the simplistic nature of the query..
Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another part of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP.
Pardon my simplistic solution, try dropping the /18, and -only- advertise the corresponding /19 from each region.
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link - I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's.
See above. K.I.S.S. (No offense intended ;)
Any help would be greatly appreciated.
Rolo !
_________________________________________________________________ Stay in touch with absent friends - get MSN Messenger http://www.msn.co.uk/messenger
On Dec 8, 2004, at 12:56 PM, Richard Irving wrote:
Please forgive the simplistic nature of the query..
Actually, it is refreshing to see _operational_ questions on the list. :-)
Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another part of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP.
Pardon my simplistic solution, try dropping the /18, and -only- advertise the corresponding /19 from each region.
This will only work if you have separate ASNs, which would be my suggested solution. In fact, even if you announce the /18 + both /19s, as long as each site as a separate ASN, it will work. If they must have the same ASN for some reason, have your upstreams send you default route as well as a full table. You will not see the "other" /19, but you will send traffic to the upstream because of the default and they will route it properly.
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link - I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's.
I've never used AS-LOOP-IN. Sorry. :( But I have used the above solution (and static defaults), and it works fine. -- TTFN, patrick
Rich LOL !! thanks for your input :)
From: Richard Irving <rirving@antient.org> To: Rolo Tomassi <rolotomassi32@hotmail.com> CC: nanog@merit.edu Subject: Re: Peering best practices advice needed. Date: Wed, 08 Dec 2004 12:56:13 -0500
Rolo Tomassi wrote:
Hi all,
Please forgive the simplistic nature of the query..
Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another part of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP.
Pardon my simplistic solution, try dropping the /18, and -only- advertise the corresponding /19 from each region.
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link - I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's.
See above. K.I.S.S. (No offense intended ;)
Any help would be greatly appreciated.
Rolo !
_________________________________________________________________ Stay in touch with absent friends - get MSN Messenger http://www.msn.co.uk/messenger
_________________________________________________________________ It's fast, it's easy and it's free. Get MSN Messenger today! http://www.msn.co.uk/messenger
Hi there, If I understand your predicament correctly, our company has a similar situation. We have two locations from which we need to advertise routes from our AS, but our internal link between these two locations is a very high cost satellite link. This means we can not afford to advertise our whole IP allocation equally from both locations. We have a /19 allocated, and we advertise both the /19 from each location, and the more specific /20 particular to each location. To circumvent the loop detection, we use the hidden Cisco command, neighbour x.x.x.x allow-as in. This allows each location to accept the remote's advertised /20 to be inserted into the routing table. Should connectivity ever be lost across the public networks in between, there is a higher cost static route over the satellite link. Perhaps in a more complex and more meshed AS, this loop dodging would be a bad thing(tm). In our simple two location, semi-discontiguous network layout, it has been a problem-free solution. Hope this helps in some way. Regards, Graham Blake SSI Micro Network Services At 10:03 AM 08/12/2004, Rolo Tomassi wrote:
Hi all,
Please forgive the simplistic nature of the query..
Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another part of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP.
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link - I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's.
Any help would be greatly appreciated.
Rolo !
_________________________________________________________________ Stay in touch with absent friends - get MSN Messenger http://www.msn.co.uk/messenger
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Rolo Tomassi Sent: Wednesday, December 08, 2004 11:04 AM To: nanog@merit.edu Subject: Peering best practices advice needed.
Hi all,
Please forgive the simplistic nature of the query..
Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another
of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP.
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link
Hello. Three options. 1. Acquire a second ASN, and announce each site's /19 from a different asn. 2. Announce each locations /19 from it's respective location, using the same asn. Use the cisco BGP command Allow-as-in to permit each AS to hear the remote site's network advertisement. 3. If the remote site will not be multihomed, ask their ISP to announce the /19 for you. My gut says that if you are advertising a block in the territory of another RIR, your irr entries will need to be correct to save filtering issues. Good Luck, Ejay part -
I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's.
Any help would be greatly appreciated.
Rolo !
____________________________________________________________ _____
Stay in touch with absent friends - get MSN Messenger http://www.msn.co.uk/messenger
Hi all,
Please forgive the simplistic nature of the query..
Basically my company is multi-homed with 2 different providers in the UK, and advertising a /18. Now some colleaguges in another part of the world want to break that /18 into two /19's and advertise one /19 and we advertise the other. This is fine, however we are NOT running IBGP in the core, therefore the UK customers in the /19 will not be able to reach the other /19 as there would be a loop detected through EBGP.
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP. I really think this is a bad idea but until we get an internal link - I dont see a way forward. So... anyone doing this currently in their network or have any "best practices" way round this. I want our company to be good Netizens but still be able to pass traffic between the 2 /19's. Well another way for solve this problem is that both parts advertise
On Wed, 2004-12-08 at 17:03 +0000, Rolo Tomassi wrote: their /19. From the transit provider take your normal routing table and a default route. The default route allows the two /19's to reach each other over the transit provider(s). -- Cheers Dg
On 8-dec-04, at 18:03, Rolo Tomassi wrote:
Now someone mentioned that we could use AS-LOOP-IN feature which will overcome this problem and allow us to route to each other via EBGP.
Some gear doesn't send updates with AS X in the path to AS X. So depending on the type of routers your upstreams have, you may not see the routing information from the other instance of your AS.
participants (7)
-
David Gethings -
Ejay Hire -
Graham Blake -
Iljitsch van Beijnum -
Patrick W Gilmore -
Richard Irving -
Rolo Tomassi