private AS numbers. how do ISP get around the small number of them?

ciscog33k

Just wondering. I figure that most large ISPs are going to have a need for more than the 64512-65534.

If I'm multihoming to a single provider as a small/medium business, I figure they'll give me a private ASN, but there's got to more than a thousand odd companies with a typical large ISP requesting them, no?

I'm hoping someone that works in a service provider environment can shed some light here because i'm curious.

stuh84

ISPs would only be BGP peering with businesses who have their own AS number, hence the use of private ASNs isn't likely to be something of their concern.

deth1k

stuh84 wrote: »

ISPs would only be BGP peering with businesses who have their own AS number, hence the use of private ASNs isn't likely to be something of their concern.

That's a wrong assumption, ISP who provide managed internet services (i.e managed CPE device) would use private AS numbers (and PA address space) on the CPE devices.

networker050184

ciscog33k wrote: »

Just wondering. I figure that most large ISPs are going to have a need for more than the 64512-65534.

If I'm multihoming to a single provider as a small/medium business, I figure they'll give me a private ASN, but there's got to more than a thousand odd companies with a typical large ISP requesting them, no?

I'm hoping someone that works in a service provider environment can shed some light here because i'm curious.

I'm not really seeing an ISP get more than 10,000 private AS customers.

deth1k

ciscog33k wrote: »

Just wondering. I figure that most large ISPs are going to have a need for more than the 64512-65534.

If I'm multihoming to a single provider as a small/medium business, I figure they'll give me a private ASN, but there's got to more than a thousand odd companies with a typical large ISP requesting them, no?

I'm hoping someone that works in a service provider environment can shed some light here because i'm curious.

Don't forget that not all businesses require their routers to run BGP, 8 times out of 10 customers are connected using just static routes.

ColbyG

networker050184 wrote: »

I'm not really seeing an ISP get more than 10,000 private AS customers.

Yea. That's quite a bit, IMO.

stuh84

deth1k wrote: »

That's a wrong assumption, ISP who provide managed internet services (i.e managed CPE device) would use private AS numbers (and PA address space) on the CPE devices.

Fair point. However, where I work, all managed CPEs are done with static routes and EIGRP, the only BGP peering we do is with either places so large they have their own ASN, or with other ISPs.

Then again, where I work isn't strictly an Internet Service Provider, but we function very much like one in most cases.

ColbyG

stuh84 wrote: »

Fair point. However, where I work, all managed CPEs are done with static routes and EIGRP, the only BGP peering we do is with either places so large they have their own ASN, or with other ISPs.

Then again, where I work isn't strictly an Internet Service Provider, but we function very much like one in most cases.

My company is dual homed to a single provider, we use a private ASN. This is more common than seem to think.

networker050184

We have a small amount of customers that we set up private ASN peering with. Usually only if they have multiple sites with fail over set up. Its easier to use BGP rather than statics with SLA to remove them and stuff like that. Most customers are just as easily set up with static routing though.

Sett

networker050184 wrote: »

I'm not really seeing an ISP get more than 10,000 private AS customers.

Well, the private AS are just over 1000, aren't they?

stuh84

I'm glad this thread proved me wrong, makes me realise that I would still be learninh completely different concepts when I hopefully one day get into an ISP.

networker050184

Sett wrote: »

Well, the private AS are just over 1000, aren't they?
Anyway, I think they can use confederations which will allow them to reuse some of the numbers.

Yeah sorry excuse the extra 0 in there.

ciscog33k

ColbyG wrote: »

My company is dual homed to a single provider, we use a private ASN. This is more common than seem to think.

+1

When my provider was running me through my options for fault tolerance, the solution involved BGP, so they would be using private ASNs. We only had one site but needed the IPs of the voip server to stay the same if one of the links went down.

Are you taking partial routes or just a default route?

ColbyG

ciscog33k wrote: »

+1

When my provider was running me through my options for fault tolerance, the solution involved BGP, so they would be using private ASNs. We only had one site but needed the IPs of the voip server to stay the same if one of the links went down.

Are you taking partial routes or just a default route?

We only take defaults. And we're not doing any engineering for inbound traffic either. It really blows.

ciscog33k

ColbyG wrote: »

We only take defaults. And we're not doing any engineering for inbound traffic either. It really blows.

Ya, sucks doesn't it? You spend all that time on BGP in the CCNP and you don't get to use it unless you work for a large enterprise or an ISP.

ColbyG

ciscog33k wrote: »

Ya, sucks doesn't it? You spend all that time on BGP in the CCNP and you don't get to use it unless you work for a large enterprise or an ISP.

I do work for a (very) large enterprise, lol. Long ago, the powers that be decided to design our internet infrastructure this way. And on the WAN side, we also only use defaults, so no BGP there either.

shodown

ColbyG wrote: »

I do work for a (very) large enterprise, lol. Long ago, the powers that be decided to design our internet infrastructure this way. And on the WAN side, we also only use defaults, so no BGP there either.

Were on differnt sides of the fence I have been trying to get rid of BGP on our network. I want to keep the EBGP, but get rid of the IBGP. So far we haven't found a decent solultion that all agree on

Paul Boz

The only people that I know of who use private AS are large companies or ISPs who only use it internally. Typically if you're large enough to be running multi-homed BGP you can get an ASN. Private BGP can also be used in large network mergers as well.

Sett

From the beginning of this year RIPE is providing only 32 bit AS numbers, I guess the count of the ASs is no longer an issue. I haven't seen any ASN32 in production yet though but they must be out there.

burbankmarc

Sett wrote: »

From the beginning of this year RIPE is providing only 32 bit AS numbers, I guess the count of the ASs is no longer an issue. I haven't seen any ASN32 in production yet though but they must be out there.

ARIN is still giving out the 2-byte version but are giving you the option for a 4-byte.

wolverene13

Where I work (3rd largest ILEC in the U.S., just behind AT&T and Verizon), not many customers peer with us via BGP. There's maybe 5 customers who peer with us per Internet Access Router in approximately 33 states, which is about 150 customers. Most customers are configured with static routes. We use BGP to announce our supernets for each market to our local peers (Level 3, Cogent, XO, etc.). From there, we connect each customer via a /30 WAN IP block that terminates on an ATM subinterface or Ethernet SVI on our end. So the router knows about the /30 because it is a connected route. We then use static routes to point traffic destined for the customer's LAN space to their side of the /30. The only customers who need to peer with us are ISPs and other large customers, like Cirque de Soliel in Las Vegas, so there's not really much use for private AS's in our design. The only place where we use private AS's is on our MPLS network, and even then, many customers can be in the same BGP AS because they have a different EIGRP AS within that market.

shodown

I know this thread is old, but for our setup

We have a route map that matches a certain IP, if we get that IP a default route is sent in to a dual homed site. We use Local Pref for a dual router setup in its own AS, or we use Weight if its just one router. Also we use AS path Prepending on the internet router to control the way the traffic comes back in, so it has to come back the same way it goes out. So we have several Private AS setups in our topology.