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Best Practices for Loopback addressing (Core routers & VPN CPE)
From: m.rapoport () completel fr
Date: Fri, 6 Jun 2003 18:05:10 +0200
I was wondering what are the choices made by Service Providers on the
The context is an IP/MPLS Backbone providing both Internet and BGP-VPN
I have 2 different cases to address :
1) Loopbacks on the backbone routers :
I have the feeling that general practice is to use public IP adresses for
However, considering that these loopbacks are only used for routing
protocols (OSPF,BGP, LDP)
and for network management (SNMP, telnet, ...) and that these addresses
don't need to visible from public Internet
(not seen in traceroute, not seen on Internet BGP announces ...) I am
use private RFC1918 for a new Backbone deployment.
N.B. : Assumption is that e-BGP sessions with Internet peers are done on
public interface IP, not on loopback IP.
Is there some specific case I am missing where public loopback IP is
required, and therefore
private adressing would break something (maybe some Carrier-to-Carrier
scenario ?) .
I also plan to use RFC1918 addresses for Internet CPE routers loopbacks.
2) Loopback on CPE routers of the MPLS VPN customers.
For this case, the issue is to assign the adresses in a global range for
all the CPE of
all the VPN customers.
In fact, all these loopback will need to be part of the Network Management
VPN for supervision needs.
Using RFC 1918 addresses might create trouble as there is a very high
chance that the VPN customers
are already using 1918 addresses, this might generate addresses conflicts.
Addresses unicity among all the customers is required due to the Network
Management VPN common
to all the customers.
Using public address guarantee unicity, but will create issues with public
registries, considering that
these addresses are used for internal needs.
I am considering to use the 198.18.0.0/15 defined in RFC 2544 and listed in
RFC 3330 as reserved for
I suppose that no VPN customer uses this prefix for its internal IP
addressing, and as these addresses don't
need to be announced on Internet.
Do you suggest to use an other prefix than 198.18.0.0/15 for this purpose ?
If you consider your adressing policy as touchy topic in terms of
security, don't hesitate to reply in private ...
- Best Practices for Loopback addressing (Core routers & VPN CPE) m . rapoport (Jun 06)