Cable&Wireless AS1273 BGP Community Strings
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 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 [email protected][email protected] 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 peer1273: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 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-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.
* We do NOT support or maintain any BGP community string
** Contact ISP to get more detail information
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