nLayer Communications AS4436
Peer BGP Policies
This section describes the policies for routing announcements received from and announced to external eBGP peers and transits.
Multi Exit Discriminator (MED) Policy
MEDs received from peers will be ignored by default, unless prior arrangements have been made to confirm the quality of the values.
MEDs are announced by default, using good aggregates and meaningful values based on IGP costs. Peers may decide to honor these MEDs at their discretion.
Damping Policy
Routing flaps from eBGP peers may be progressively dampened, based on prefix lengths as describe in the table below. This is done to protect our network from the instabilities of other announcements on the Internet.
Prefix Length Filtering
Announcements received from peers are filtered against a list of bogon blocks, as well as by prefix length. The shortest prefix length which will be accepted from any network is a /5, the longest prefix length which will be accepted is a /24.
Outbound announcements from nLayer will never exceed /24 in length. All routes announced will be registered in the Internet Routing Registry (IRR) databases under the as-set AS-NLAYER.
Damping Policy Prefix Length Half-life Reuse Limit Suppress Limit Max Suppress /24 or longer 10 7000 10000 15 /20 – /23 5 7000 10000 10 /17 – /19 3 7000 10000 5 /16 or shorter 1 10000 15000 2
Customer BGP Policies
This section describes the policies for routing announcements received from and announced to customers speaking BGP, including information on how customers may use BGP community tags to influence nLayer routing policy for their announcements.
Receivable BGP Communities
Customers may influence nLayer routing policies by a number of BGP community tags which may be set on routes which they announce. These tags can control the propagation of routes, adjust the localpref assigned to them, and even null route traffic.
Announced BGP Communities
All routes announced to customers are tagged with the following information:
4436:TCRI
T The type of relationship that the route was learned through.
C The continent where the route was learned.
R The region where the route was learned, if in the US.
I Internal usage only.
IRR Filtering
All customers announcements are filtered against Internet Routing Registry (IRR) databases. BGP speaking customers will be expected to maintain current and correct IRR entries.
All nLayer announcements will be recorded under the as-set AS-NLAYER.
Receivable BGP Communities
Receivable BGP Communities BGP Community String
Action 4436:1 Prepend 4436 to route 4436:2 Prepend 4436 4436 to route 4436:3 Prepend 4436 4436 4436 to route 4436:50 Set local preference to 50 4436:100 Set local preference to 100 4436:150 Set local preference to 150 4436:200 Set local preference to 200 4436:250 Set local preference to 250 4436:300 Set local preference to 300 4436:555 Null route (discard) traffic 4436:666 Do not export to anyone 4436:777 Do not export to transits 4436:888 Do not export to peers 4436:999 Do not export to customers
Special BGP Communities BGP Community String
Action ASN:1 Prepend 4436 to ASN ASN:2 Prepend 4436 4436 to ASN ASN:3 Prepend 4436 4436 4436 to ASN ASN:666 Do not announce to ASN
Announced BGP Communities Value Type Continent US Region 1 Public Peer North America NYC 2 Private Peer Europe IAD 3 Transit Asia ATL 4 Customer Australia ORD 5 Internal South America KCY 6 Middle East DFW 7 SEA 8 SJC 9 LAX
Local Preferences Localpref Description 50 Depreferenced transit route 100 Default transit route 150 Depreferenced peering route 200 Default peering route 250 Depreferenced customer route 300 Default customer route 400 Default internal route
**Information source below to see recent update
http://www.nlayer.net/network/bgppolicies/
Applying BGP Community string with sample configuration
1. Get the latest BGP community string from your ISP/upstream provider or check new.CiscoNET.com web site.2. Pick the best BGP community string for your traffic shaping plan (mainly incoming traffic). Most of ISPs are providing BGP community string with local preference and AS prepending option. Cannot tell which one is better than the other. It will depend on your global traffic shaping plan.
3. Follow the below commands ( Cisco only )
The below Sample configuration will tag the 10.0.0.0/24 route with [ISP AS]:120 or [ISP AS]:3 and will not tag any other routes.
router#config t
router(config)#ip bgp-community new-format
router(config)#access-list 10 permit 10.0.0.0 0.0.0.255
router(config)#access-list 10 deny anyrouter(config)#route-map [to-ISP] permit 10
router(config-route-map)#match ip address 10
router(config-route-map)#set community [ISP AS]:120 <—- using Local Preferenceor
router(config-route-map)#set community [ISP AS]:3 <——- using AS prepending
router(config-route-map)#route-map [to-ISP] permit 20
router(config-route-map)#exitrouter(config)#router bgp [xxxx] <——————————- xxxx = customer’s ASN
router(config-router)#neighbor x.x.x.x send-community
router(config-router)#neighbor x.x.x.x route-map [to-ISP] out
router(config-router)#exit
router(config)#exit
router#copy running-config startup-config4. And then, go to www.CiscoNET.com and pick one of route server on the map to see your announcement. If you are using AS prepending option, you will see your AS prepends on route servers. Sometime you might not see your route with particular ISP path.
In most of case it might not be any routing problem, just the route path was dropped at somewhere by BGP best path selection scheme. Try Oregon route server, if you can see your route. The Oregon route server is providing many possible and available paths between BGP speakers and neighbors.
If you don’t see your route on there? check other route servers and also check your
BGP configuration. You might need to contact your upstream provider to check what they are learning BGP route from you.
* We do NOT support or maintain any BGP community string
** Contact ISP to get more detail information
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