BGP
Manipulating BGP Path Decision Process
The “no-export”/”no-advertise” community-strings could be useful if you need to configure filtering but without using ACL’s etc.
When using the “local-AS” community, I’ve found that if you put this in a route-map and then activate it with the “neighbor 1.2.3.4 route-map LOCAL_AS in ” command, if the neighbor is a true eBGP neighbour the “local-as” community-string won’t be attached to the required prefix. I tested this over and over, and ensured I had the “neighbor 1.2.3.4 send-community” configured. When I then changed the route-map to point to a sub-confed eBGP neighbour (neighbor 2.3.4.5 route-map LOCAL_AS out), the sub-confed eBGP neighbour then sees the prefix with the community-string attached:
R3#sh ip bgp 204.12.1.0
BGP routing table entry for 204.12.1.0/24, version 7
Paths: (1 available, best #1, table Default-IP-Routing-Table, not advertised outside local AS)
Flag: 0×880
Not advertised to any peer
3
155.1.13.1 from 155.1.13.1 (150.1.1.1)
Origin IGP, metric 0, localpref 100, valid, confed-internal, best
Community: local-AS
I’ve also covered about 2 thirds of the IEWB Vol I BGP Labs.
IPv6
RIPng
Under the interface “ipv6 rip (name) enable”
Uses port UDP 521 and multicasts to FF02::9
OSPFv3
Under the interface use ipv6 ospf (Process ID) area (id)
Or use the same under the routing process as for OSPFv2
The router-id is still an IPv4 address!!
Multicasts to FF02::5/6
Just like OSPFv2 the following networks types don’t modify the next hop:
Broadcast
Non-Broadcast
With layer 2 to layer 3 mapping over non-broadcast networks, the mapping needs to be configured to point to the neighbours Link Local interface ipv6 address. To get this info, use “show ipv6 interface brief”:
R5(config-if)#do sh ipv6 inter bri
FastEthernet0/0 [administratively down/down]
Serial0/0 [up/up]
FE80::20F:8FFF:FE0F:32C0 2001:150:1::5
FastEthernet0/1 [administratively down/down]
Serial0/1 [administratively down/down]
Serial0/2 [administratively down/down]
Loopback0 [up/up]
FE80::20F:8FFF:FE0F:32C0
2001:150:1:5::5
R5(config-if)#
Just copy and paste the Link Local address onto the OSPF neighbour you want it to peer to using the “frame-relay map ipv6″ command.
On NBMA network types with OSPFv3, you will need to put the following under the interface:
ipv6 ospf neighbor FE80::209:E8FF:FED1:62A0 - must be the Link Local Address!!!! So you MUST have a layer 2 to layer 3 to the neighbours Link Local Address!!!!
I didn’t do as much as I planned to today. That was down to lack of motivation, I couldn’t get my arse into gear and study some more. I will make up for that tomorrow!!
I will continue and finish off IPv6 automatic/manual tunnels and I should hopefully finish the IEWB Vol I BGP Labs.
Amount of time studying today - 5hrs 20 mins
Total Studying hours so far since starting this blog - 77hrs 47mins
