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BGP Communities String

Cable & Wireless AS1273

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Instroduction

Cable & Wireless allows customers to control certain traffic flows off-net with the implementation of BGP community attribute values that prepend route/prefix paths with additional AS hops. These BGP community attribute values, which the customer applies, affects the way C&W peers choose the degree of preference of a given prefix/route, because the number of AS hops within the route-path has been lengthened.

Format

The format for the second component of customer route community number (after 1273:) is set at five digits. This fixed length allows regular expressions to be used in applying a defined number of prepends to a given route/prefix path. This format is 1273:3PPPN, where the fields are coded in the following way. (Note: The first digit of the second component is always "3" then followed by variables of the "PPP" and "N" variables which are defined in the following tables.)

Variables

The "PPP" variable cross references off-net connections of C&W, defined in the following tables. (Note, this will always be a three digit value.)

European peer PPP codes: (PPP values 100-200)

PPP Code	Peer Name	Peer AS Number
000	All Peers & upstreams
200	MCI Europe	AS702/AS12702
199	Global Crossing	AS3549
198	SWIPNET	AS1257
197	Tiscali	AS3257
196	Telia	AS1299
195	France Telecom	AS5511
194	Swisscom	AS3303
193	COLT	AS8220
192	Eircom	AS5466
191	Abovenet	AS6461
190	DTAG	AS3320
189	Arcor Mannesmann	AS3209
188	AT&T EMEA	AS2686
187	DFN	AS680
186	Global Access	AS13129
185	Globix	AS4513
184	I-Primus	AS5427
183	Mobilcom	AS5430
182	Regionet	AS8319
181	Telenor	AS8210
180	Tesion	AS15717
179	BT Ignite	AS8472
178	Telefonica	AS12956
177	Microsoft	AS8086
176	Teleglobe	AS6453
175	Reach	AS4637
174	KPN Eurorings	AS286
173	BBC	AS2818
172	BT	AS5400
171	Bredband	AS8642
170	Yahoo Europe	AS15635
169	MANDA	AS8365
168	AUCS/Infonet	AS3300
167	UPC Distribution Services	AS6830
166	UTA.AT United Telekom Austria	AS8437
165	Cablecom GmbH	AS8404
164	Verio	AS2914
163	LINX	AS5459
162	Net Access	AS8001
161	Telecom Italia Sparkle	AS6762
160	Interroute	AS8928
159	R-KOM Regensburger Telekommunikation	AS12611
158	Cogent	AS174
157	Schlund	AS8560
156	Hurricane Electric	AS6939
155	SongNetworks	AS3246
154	PCCWBtN	AS3491
153	Lambdanet	AS13237
152	Versatel	AS8881
151	Akamai Technologies	AS20940
150	Google	AS15169
149	Cable & Wireless UK	AS5388
148	Sara	AS1126
147	Giganews	AS30094

American peer PPP codes: (PPP values 001-099)

PPP Code	Peer Name	Peer AS Number
099	TTSG Internet Services	AS13945
098	Datapipe	AS14492
097	ISPRIME	AS23393
096	Primus Canada	AS6407
094	HopOne	AS14361
092	nLayer	AS4436
091	Webair	AS27257
090	Ezzi.net	AS15149
089	Tellurian	AS10848
088	DALnet	AS31800
087	New York Internet	AS11403
086	Microsoft	AS8075
084	eBay	AS11643
083	SBC Internet	AS7132
082	RCN	AS6079
081	Yahoo America	AS10310
080	PCH	AS42
079	PCH	AS3856
078	Cox	AS22733
077	Akamai Technologies	AS12222
076	Rogers Cable	AS812
075	Rackspace.com	AS27357
074	MTS-Allstream Inc	AS15290
073	Group Telecom	AS6539
072	Adelphia communication	AS19548
070	Shaw Cablesystems/Big Pipe Inc.	AS6327
071	Broadwing	AS6395
069	Thorn Communications	AS12124
068	Limelight Networks	AS22822
067	Stealth Communications	AS8002
066	TMT Warner	AS4323
065	TDS	AS4181
064	Host.net	AS13645
063	Terremark	AS23148
062	Prolexic	AS32787
061	Renesys	AS64597
060	Mzima	AS25973
059	Peer1	AS13768
058	Atlantech Online	AS7784
057	Netifice Communications	AS4565
056	NTELOS	AS7795
055	Electric Lightwave	AS5650
054	ESnet	AS293
053	IIJ	AS2497
052	TWGATE	AS9505
051	China Telecom	AS4134
050	Doubleclick	AS6432
049	McLeod USA	AS7228
048	Earthlink	AS4355
047	Electronic Arts	AS14891
046	Carpathiahost	AS29748
045	Edge Networks	AS19029
044	GNAP	AS1784
043	Real Connect	AS16559
042	BBC	AS9156
041	Walmart	AS17374
040	Comsat International	AS7908
039	Cable Vision	AS6128
038	Servercentral	AS23352
037	WV Fiber	AS19151
036	VOXEL	AS29791
035	Choopa	AS20473
034	US LEC	AS1785
010	IDC Japan	AS4694

Peering point PPP codes: (PPP values 970-989)

PPP Code	Peering Point Name	Peering Point Location
989	AMSIX	Amsterdam, NL
988	DECIX	Frankfurt, DE
987	INXS-HBG	Hamburg, DE
986	INXS-MUC	Munich, DE
985	LINX	London, UK
984	PARIX	Paris, FR
983	INEX	Dublin, IE
975	NAP of the Americas	Miami, FL, US
974	PAIX	Palo Alto, CA, US
973	LAIIX	Los Angeles, CA, US
972	Equinix	Ashburn, VA, US
971	PAIX NY	New York, NY, US
970	NYIIX	New York, NY, US

Upstream PPP codes: (PPP values 990-998)

PPP Code	Upstream Name	Upstream AS number
998	Savvis Communications	AS3561
996	Level 3	AS3356
995	Sprint	AS1239

The "N" variable cross references the number of prepends, defined in the following table.
Allowable values of N:

Value	Effect
0	Do not announce to selected peer
1	Prepend 1x to selected peer
2	Prepend 2x to selected peer
3	Prepend 3x to selected peer
9	Announce to this peer only (also announces to customers)

Examples

1273:32000 - Do not announce to MCI Europe (AS702)
1273:31752 - Prepend twice to Reach (AS4637)
1273:39963 - Prepend three times to Level 3 Upstream connection (AS3356)

Please note that mixing a 'prepend to IXP' BGP community with a 'prepend to specific peer' BGP community may not have the intended effect. Prepending once to LINX and once to BT will lead to the route being prepended once to BT at LINX, whereas prepending an unequal number of times to an IXP and a peer at that IXP will lead to the sum of the prepends being added (e.g. prepending once to LINX and twice to BT will lead to three prepends being sent to BT at LINX). For this reason it is not recommended to mix specific and general prepend BGP communities on the same routes.

C&W Blackhole BGP Community Attribute Values (1273:666)

For customers that have a host or block under a DDoS, the affected host/block can be advertised to AS1273 with BGP community string 1273:666. This will cause all traffic to that host/block to be black-holed at the core of the AS1273 network.This action will trigger emails sent to the appropriate security and operations groups for notification purposes. After advertising the prefix with 1273:666, the customer may open a ticket to request further assistance with their Cable & Wireless management agency, or open a ticket via email to This e-mail address is being protected from spam bots, you need JavaScript enabled to view it Once the attack has been mitigated, the customer will be responsible for removing the prefix from being advertised. Cable & Wireless will not be held responsible for customers who errantly advertise prefixes with the blackhole community string.

C&W local preference alteration BGP communities

The local-preference hierarchy within C&W AS1273 is as follows

Value	Effect
100	Customers (BGP and injected static)
90	Backup customer connections
80	Peers
75	Transit/Upstream Providers
70	Last resort customer connections

The following BGP communities can be sent to influence the local-preference of a customer route

BGP Community String	Effect
1273:90	Sets local preference value within AS1273 to 90
1273:80	Sets local preference value within AS1273 to 80
1273:70	Sets local preference value within AS1273 to 70
1273:no-export	Prevents this route from being announce to any AS1273 EBGP peer
1273:no-advertise	Prevents this route from being announced to any AS1273 EBGP or IBGP peer

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 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 any

router(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 Preference

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)#exit

router(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-config

4. 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.

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