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  1. #1

    Setting up BGP for my tiny little datacenter

    Newbie questions about BGP... I've got a T1 from Verizon Business (formerly Worldcom/MCI) and another T1 from Megapath. I've always wanted to set up BGP with these two circuits for inbound redundancy to my half-dozen web servers, but was never sure where to start. Megapath sounds kind of clueless about setting up BGP with another ISP. I haven't discussed it with Verizon yet.

    I've got 32 IPs with Verizon and a Cisco 2620 router. This is my "primary" T1. I've got 16 IPs with Megapath and a Netopia R5300. This is my backup T1. Both are provisioned for full 1.5Mbps.

    Do I need to get 32 IPs from Megapath so the block size is the same as Verizon?

    Do I need to replace the Megapath router with a matching Cisco 2620?

    I need to get an ASN, correct? Is ARIN going to laugh because it's a small block of 32 IP's?

    I don't have a clue about Cisco IOS - I'm sure there are network consultants available that would set up BGP on the routers for a fee?

    What kind of red tape can I expect getting two competing ISPs to work with each other on this?

    Thanks!

    -- Paul

  2. #2
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    To announce your IPs to the world and not get filtered, you will need at least a /24 (256IPs). Both your ISP probably would not speak bgp to you for T1s.

  3. #3
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    You will have trouble announcing your existing IP addresses since most networks filter any prefixes longer than /24 (256 IP Addresses). If you are planning to use BGP to establish redundancy, you will need to obtain an ASN from ARIN. You will also need to obtain a /24 from one of your providers (if you can justify its use).

    Both ISP's should be willing to work with you on setting up their end for BGP.

    You may want to contact a network consultant to see what they recommend for a router.
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  4. #4
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    ARIN will not laugh when you submit your request if you specify a block of 32 IP addresses. What address blocks you announce is generally outside the scope of the question, "do you need a globally unique AS number?"

  5. #5
    Along with the ASN, do I also need to request a block of portable IPs from ARIN? Looks like a block of 256 IPs is the recommended minimum?

  6. #6
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    You need to request the addresses from one of your upstream providers. You do not meet the minimum requirements for an allocation directly from ARIN. You must have a need for at least a /23 of addresses before going directly to ARIN.

    Multi-homed:

    Organizations requesting an allocation under the IPv4 Multi-homing policy must prove an intent to multi-home, demonstrate utilization for at least a /23-worth of IP address assigned by upstream providers, supply reassignment information for its current address space; and provide 3-, 6-, and 12-month utilization projections.

    In addition, the organization must agree that the requested IPv4 address space will be used to renumber out of its current address space, and that once the renumbering is complete, the organization will return its entire original address space to its upstream provider(s). Additional space will not be allocated until this is completed. Organizations that qualify under this policy may also qualify and request space under ARIN's general IPv4 allocation policy.

    The exact requirements are detailed in Section 4.2.2.2 of the Number Resource Policy Manual.
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  7. #7
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    Building on gps's post, it's worth noting ARIN has a published policy allowing one of your upstreams to reassign you a /24 solely for establishing BGP multi-homedness, with no other justification needed (e.g., hostcounts).

  8. #8
    FWIW, in the ARIN fee schedule they mention a "micro-allocation" of /24 so I got the impression that was something that was possible ...

    Ok, so I would be requesting a "portable" block from one of my upstream providers? This would give me IPs in the 209.x.x.x range? Or would Verizon (UUNet/Alternet) give me something out of their 65.x.x.x block? Once I have this in hand, I then go to my other upstream provider to coordinate BGP with the first provider?

    Do I still need an ASN ?

  9. #9
    Join Date
    Jul 2005
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    To answer your last question first, you need a globally unique AS number if your plan is to originate a route announcement (of a /24, for example, reassigned to you by Verizon Business) and exchange that routing information with more than one provider or peer via BGP. (In other words, "yes".)

    To respond to your first point, ARIN provides micro-allocations of IPv4 and IPv6 addresses to:

    * critical internet infrastructure networks
    * public exchange points
    * networks requiring non-routed IPv6 addresses in their core unique from their existing edge IPv6 addressing topology

    Critical internet infrastructure networks include core DNS service providers (e.g. ICANN-sanctioned root, gTLD, and ccTLD operators) as well as the RIRs and IANA.

  10. #10
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    You definitely want the /24 from MCI/UUNet, *not* MegaPath. As you indicated, they're probably rather clueless about BGP. MCI will be assigning you a /24 out of a /14 - /16 most likely, and their aggregated prefix will be announced to the global Internet as such. Your /24 announcement to MegaPath will undoubtedly get filtered by some of thebigger ASNs (for example, Verio will not accept anything into their routing tables smaller than a /22 unless your /24 was assigned directly by ARIN). So you won't have true incoming redundancy but you'll probably have upwards of 80 or 90% coverage of the Internet in the event of an MCI outage. But you definitely want MCI's IPs and not the other way around, as MCI will likely be the more reliable of the two.

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  11. #11
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    BGP brings about more problems than it fixes in a lot of cases. Are the T1s so unreliable as to need BGP?

  12. #12
    Quote Originally Posted by CrystalVPS
    BGP brings about more problems than it fixes in a lot of cases. Are the T1s so unreliable as to need BGP?
    The T1s are actually very reliable. It's only in the last couple weeks that we've had latency issues with the Verizon (MCI/UUnet) T1 due to a problem with a DS3 farther upstream. Thus my renewed interest in redundancy.

    I am giving the BGP thing second thoughts, as you say might be more trouble than it's worth... Verizon can handle the BGP request, but MegaPath cannot. So I'd probably have to cancel my service with MegaPath and find another provider (like XO Communications who has a BGP Policy plainly stated on their website, imagine that!). But I really don't want to go T1 shopping again just for this. Talking to T1 salesmen is about as much fun as going to the dentist.
    Last edited by paule123; 12-31-2006 at 01:05 PM.

  13. #13
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    BGP doesn't automatically fix latency - often it takes more effort, as you have more providers to constantly check. We have 5 or 6 providers and have a nice nagios setup monitoring latency and more. BGP isn't worth the effort until you are doing a reasonable amount of traffic in my opinion.

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