Mention that DN42_REGION should not be modified in transit

James Lu commited 2021-12-19 18:20:51 -0800 commit 0eb94c89536af28aab8c7a5314b401d327762087

howto/Bird-communities.md

@@ -78,8 +78,10 @@ According to [this mail](https://lists.nox.tf/pipermail/dn42/2015-December/00125

 You need to add following lines to your config(s):

 - `define DN42_REGION = $VALUE_FROM_ABOVE` to your node's config (where OWNAS and OWNIP are set)

-- `if source = RTS_STATIC then bgp_community.add((64511, DN42_REGION));` 

+- `if source = RTS_STATIC then bgp_community.add((64511, DN42_REGION));`

 just above `update_flags` in `dn42_export_filter` function

+- Unlike the other community values, **the DN42_REGION community should only be set on routes originating from your network!** (This is what the `source = RTS_STATIC` check does).

+ - Otherwise, if you export routes across multiple regions within your network, you may be sending incorrect origin information to other peers.

 ## Example configurations

...	...	@@ -78,8 +78,10 @@ According to [this mail](https://lists.nox.tf/pipermail/dn42/2015-December/00125
78	78
79	79	You need to add following lines to your config(s):
80	80	- `define DN42_REGION = $VALUE_FROM_ABOVE` to your node's config (where OWNAS and OWNIP are set)
81		-- `if source = RTS_STATIC then bgp_community.add((64511, DN42_REGION));`
	81	+- `if source = RTS_STATIC then bgp_community.add((64511, DN42_REGION));`
82	82	just above `update_flags` in `dn42_export_filter` function
	83	+- Unlike the other community values, the DN42_REGION community should only be set on routes originating from your network! (This is what the `source = RTS_STATIC` check does).
	84	+ - Otherwise, if you export routes across multiple regions within your network, you may be sending incorrect origin information to other peers.
83	85
84	86
85	87	## Example configurations