Action BGP Communities can be used to control various functions of the route server. With these communities, you can:
- control the redistribution of advertised prefixes, based on an ASN
- control the redistribution of advertised prefixes, based on geolocation
- control the redistribution of advertised prefixes, based on ASN and geolocation
- prepend your own ASN up to three times, and
- trigger the calculation of a new alternate path (if available) for your advertised prefixes before commencing maintenance.
Please note that if the $ASN is a four byte AS number you have to use the BGP Large Communities.
Control of prefix redistribution
You can control which BGP announcements you send to the route servers are redistributed to other peers. This can be done based on the following criteria:
- ASN
- Switch
- Metro region
- Country
- Continent
The redistribution can be controlled with BGP Communities and BGP Large Communities .
The following table gives an overview of available options and their corresponding BGP Communities. The according values for $SWITCH, $METRO, $COUNTRY, $CONTINENT are available here . If two or more BGP (large) Communities contradict each other, the community with the lowest evaluation order is processed.
| EVALUATION ORDER | GROUP | ACTION |
BGP STANDARD COMMUNITY (RFC 1997) |
BGP LARGE COMMUNITY (RFC 8092) |
|
1 |
Well-known |
65535:65281 |
/ |
|
|
65535:65282 |
/ |
|||
|
2 |
ASN based |
Do not redistribute to $ASN |
0:$ASN |
50263:0:$ASN |
|
3 |
Redistribute to $ASN |
50263:$ASN |
50263:1:$ASN |
|
|
4 |
Do not redistribute to $ASN in $SWITCH |
|
50263:921$SWITCH:$ASN |
|
|
5 |
Redistribute to $ASN in $SWITCH |
|
50263:911$SWITCH:$ASN |
|
|
6 |
Do not redistribute to $ASN in $METRO |
|
50263:922$METRO:$ASN |
|
|
7 |
Redistribute to $ASN in $METRO |
|
50263:912$METRO:$ASN |
|
|
8 |
Do not redistribute to $ASN in $COUNTRY |
|
50263:923$COUNTRY:$ASN |
|
|
9 |
Redistribute to $ASN in $COUNTRY |
|
50263:913$COUNTRY:$ASN |
|
|
10 |
Do not redistribute to $ASN in $CONTINENT |
|
50263:924$CONTINENT:$ASN |
|
|
11 |
Redistribute to $ASN in $CONTINENT |
|
50263:914$CONTINENT:$ASN |
|
|
12 |
Switch based |
Do not redistribute to $SWITCH |
|
50263:921:$SWITCH |
|
13 |
Redistribute to $SWITCH |
|
50263:911:$SWITCH |
|
|
14 |
Metro based |
Do not redistribute to $METRO |
|
50263:922:$METRO |
|
15 |
Redistribute to $METRO |
|
50263:912:$METRO
|
|
|
16 |
Country based |
Do not redistribute to $COUNTRY |
|
50263:923:$COUNTRY |
|
17 |
Redistribute to $COUNTRY |
|
50263:913:$COUNTRY |
|
|
18 |
Continent based |
Do not redistribute to $CONTINENT |
|
50263:924:$CONTINENT |
|
19 |
Redistribute to $CONTINENT |
|
50263:914:CONTINENT |
|
|
20 |
General |
Do not distribute |
0:50263 |
50263:0:0 |
|
21 |
Redistribute to all (default) |
50263:50263 |
50263:1:0 |
|
|
|
|
|
|
|
More than one of the aforementioned BGP Communities and BGP Large Communities can be added to a single BGP announcement.
All BGP Communities and BGP Large Communities that are not listed above are not touched by the route servers and transparently re-distributed. For backwards compatibility, routes with no community at all are distributed to all peers as well.
You can check this in the 1-IX EU Looking Glass . If you type your ASN into the global search field, you will find all matching prefixes from all 1-IX EU route servers.
By clicking on a prefix, you get the prefix information dialogue with details (BGP Communities etc.)
AS path prepending
You can use BGP communities to prepend your own ASN up to three times. This can be done to all other peers or selectively to only certain peers.
| BGP STANDARD COMMUNITY (RFC 1997) | BGP LARGE COMMUNITY (RFC 8092) | |
|
Prepend once selectively |
65001:$ASN |
50263:65001:$ASN |
|
Prepend twice selectively |
65002:$ASN |
50263:65002:$ASN |
|
Prepend three times selectively |
65003:$ASN |
50263:65003:$ASN |
Filtering Example 1
If you would like to redistribute your routes to only $COUNTRY = Ukraine and $COUNTRY = Slovakia and filter to all the others, you can put Do not distribute (50263:0:0) plus Redistribute to Ukraine(50263:913:804) and Redistribute to Slovakia(50263:913:703)
set policy-options community 1-IX-EU-export-Ukraine members large:50263:913:804
set policy-options community 1-IX-EU-export-Slovakia members large:50263:913:703
set policy-options community 1-IX-EU-no-export-all members large:50263:0:0
set policy-options policy-statement export-1-IX-EU term 1 then community set 1-IX-EU-no-export-all
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-export-Ukraine
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-export-Slovakia
set policy-options policy-statement export-1-IX-EU then reject
show |compare
[edit policy-options]
+ policy-statement export-1-IX-EU {
+ term 1 {
+ then {
+ community set 1-IX-EU-no-export-all;
+ community add 1-IX-EU-export-Ukraine;
+ community add 1-IX-EU-export-Slovakia;
+ }
+ }
+ then reject;
+ }
[edit policy-options]
+ community 1-IX-EU-export-Ukraine members large:50263:913:804;
+ community 1-IX-EU-no-export-all members large:50263:0:0;
Filtering Example 2
If you would like to redistribute your routes to all peers except $CONTINENT=Africa ( 50263:924:2 ), except $COUNTRY=Ukraine ( 50263:923:804), but redistribute to $METRO=Odesa(50263:912:105) (which is in Ukraine) and redistribute to $METRO=Lviv(50263:912:102) (which is in Ukraine)
set policy-options community 1-IX-EU-no-export-Ukraine members large:50263:923:804
set policy-options community 1-IX-EU-export-Ukraine-Odesa members large:50263:912:105
set policy-options community 1-IX-EU-export-Ukraine-Lviv members large:50263:912:102
set policy-options community 1-IX-EU-no-export-Africa members large:50263:924:2
set policy-options policy-statement export-1-IX-EU term 1 then community set 1-IX-EU-no-export-Africa
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-no-export-Ukraine
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-export-Ukraine-Odesa
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-export-Ukraine-Lviv
set policy-options policy-statement export-1-IX-EU term 1 then accept
set policy-options policy-statement export-1-IX-EU then reject
show | compare
[edit policy-options]
+ policy-statement export-1-IX-EU {
+ term 1 {
+ then {
+ community set 1-IX-EU-no-export-Africa;
+ community add 1-IX-EU-no-export-Ukraine;
+ community add 1-IX-EU-export-Ukraine-Odesa;
+ community add 1-IX-EU-export-Ukraine-Lviv;
+ accept;
+ }
+ }
+ then reject;
+ }
[edit policy-options]
+ community 1-IX-EU-export-Ukraine-Lviv members large:50263:912:102;
+ community 1-IX-EU-export-Ukraine-Odesa members large:50263:912:105;
+ community 1-IX-EU-no-export-Africa members large:50263:924:2;
+ community 1-IX-EU-no-export-Ukraine members large:50263:923:804;
Filtering Example 3
If you would like to redistribute your routes to $ASN=24940 in $METRO=Amsterdam, but not redistribute your routes to $ASN=24940 in $COUNTRY=Netherlands, and not redistribute your routes to $ASN=24940 in $COUNTRY=Germany, and redistribute to $ASN=32590 in $METRO=Warsaw, but not redistribute your routes to $ASN=32590 in $COUNTRY=Poland
set policy-options community 1-IX-EU-AS24940-export-Amsterdam members large:50263:912110:24940
set policy-options community 1-IX-EU-AS24940-no-export-Netherlands members large:50263:923528:24940
set policy-options community 1-IX-EU-AS24940-no-export-Germany members large:50263:923276:24940
set policy-options community 1-IX-EU-AS32590-export-Warsaw members large:50263:912107:32590
set policy-options community 1-IX-EU-AS32590-no-export-Poland members large:50263:923616:32590
set policy-options policy-statement export-1-IX-EU term 1 then community set 1-IX-EU-AS24940-export-Amsterdam
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-AS24940-no-export-Netherlands
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-AS24940-no-export-Germany
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-AS32590-export-Warsaw
set policy-options policy-statement export-1-IX-EU term 1 then community add 1-IX-EU-AS32590-no-export-Poland
set policy-options policy-statement export-1-IX-EU term 1 then accept
set policy-options policy-statement export-1-IX-EU then reject
show | compare
[edit policy-options]
+ policy-statement export-1-IX-EU {
+ term 1 {
+ then {
+ community set 1-IX-EU-AS24940-export-Amsterdam;
+ community add 1-IX-EU-AS24940-no-export-Netherlands;
+ community add 1-IX-EU-AS24940-no-export-Germany;
+ community add 1-IX-EU-AS32590-export-Warsaw;
+ community add 1-IX-EU-AS32590-no-export-Poland;
+ accept;
+ }
+ }
+ then reject;
+ }
[edit policy-options]
+ community 1-IX-EU-AS24940-export-Amsterdam members large:50263:912110:24940;
+ community 1-IX-EU-AS24940-no-export-Germany members large:50263:923276:24940;
+ community 1-IX-EU-AS24940-no-export-Netherlands members large:50263:923528:24940;
+ community 1-IX-EU-AS32590-export-Warsaw members large:50263:912107:32590;
+ community 1-IX-EU-AS32590-no-export-Poland members large:50263:923616:32590;