At 07:12 PM 9/30/2002 +0000, MADMAN wrote: >Interesting. I don't work for an ISP bt have worked with many and I >have only ran into one that ran an IGP with it's customers and I was >suprised. My ancedotal evidence suggests that the vast majority either >run BGP or statics to announce customer networks. I know there are >plenty of ISP engineers out there and can confirm/rip my conjecture ;) > > Dave
Best practises would dictate the use of static or a distance vector variant IGP for customer connections. The lack of import filtering capability in Link State protocols presents a very dangerous situation for the ISP. In general, ISP's are very paranoid about customers (and peers/providers alike) and take all means necessary to protect themselves from misbehaving external peers (IP peers in this general case) BGP naturally provides the most policy rich tool set for those applications where static routing will not suffice. I find RIP to be a comfortable variant for those multihomed customers who simply will not turn up BGP, though I'd still prefer to have the BGP discussion one last time with them prior to doing using it. Of course, linking one's main IGP to a customers is a really silly idea which I think everyone grasps ;) >Mike Bernico wrote: > > > > I'm not sure I'm in complete agreement. The network I work for has several > > distribution routers that contain around 1000 T1 speed customers. If we > > were to static route each of their networks it would add about 1000 to 1500 > > lines of router configuration to the router. That would definately add to > > our maintenance and provisioning work and make troubleshooting harder on >our > > techs. While I agree statics are probably the most stable way, I'm not > > sure it's necessarily the best way to aggrigate high volumes of customers. > > We currently use EIGRP at the edge with the stub command, OSPF or IS-IS > > would work just as well. Regardless, we would never let our IGP, that > > extends to the CE router, touch their IGP. About 98% of our customers are > > not BGP customers though. > > > > YMMV > > Mike > > > > ------------------- > > Mike Bernico [EMAIL PROTECTED] > > Illinois Century Network http://www.illinois.net > > (217) 557-6555 > > > > > -----Original Message----- > > > From: Howard C. Berkowitz [mailto:[EMAIL PROTECTED]] > > > Sent: Monday, September 30, 2002 11:37 AM > > > To: [EMAIL PROTECTED] > > > Subject: Re: OSPF for ISPs [7:54540] > > > > > > > > > At 2:58 PM +0000 9/30/02, Don wrote: > > > >Rather than run OSPF to customers, it is generally much > > > better to have > > > >them use a default route to the ISP and for the ISP to run > > > static routes to > > > >the customer. OSPF to the customer is a huge land mine for > > > the ISP and > > > >should be avoided in almost every case. > > > > Don > > > > > > I agree completely with Don that an ISP _never_ should link its IGP > > > to that of the customer. Don't fall into the trap of assuming that > > > BGP needs a full routing table or will consume excessive resources. > > > > > > I remain confused why a default route wouldn't serve, unless there > > > are multiple connections between the ISP and customer. By "send the > > > block to the customer," do you mean the block is in the customer's > > > space? You could certainly use a second static route, which can be > > > generated automatically as part of your address assignment (see my > > > NANOG presentation, > > > http://www.nanog.org/mtg-9811/ppt/berk/index.htm). > > > > > > If that's not appropriate, have the customer announce his two blocks > > > to you with BGP and receive default from your BGP. > > > > > > > > > > > > > > >""Chris Headings"" wrote in message > > > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > >> Good morning all. I was wondering if someone could lend > > > me a little help > > > >> about engineering OSPF in the backbone for an ISP > > > network. I just had a > > > >> couple of questions and hopefully someone can give me > > > some guidance.or > > > >even > > > >> some CCO links with some specific examples or better yet > > > any material > > > >> anywhere. > > > >> > > > >> Say, for example, that a customer has a small block of IP's and a > > > >> distribution router knows where that block is, via a > > > connected route, > > > like > > > >a > > > >> /30 on a serial link. But later down the line the > > > customer requests an > > > >> additional block of 64 IP addresses, what is the best way > > > to send this > > > >block > > > >> to the customer? Do I need to run OSPF on the customer > > > equipment? If > > > the > > > >> customer router is not running OSPF, how do the routers > > > know how to get > > > to > > > >> this destination? I assume via static routing??? > > > >> > > > >> Thanks as always. > > > >> > > > > > Chris >-- >David Madland >CCIE# 2016 >Sr. Network Engineer >Qwest Communications >612-664-3367 > >"You don't make the poor richer by making the rich poorer." --Winston >Churchill Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=54877&t=54540 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
