Best Practices for Loopback addressing (Core routers & VPN CPE)
marc at sniff.de
Sun Jun 8 12:27:47 UTC 2003
Another argument for public loopback/link addresses: merging networks.
Fairly bad when you plan to merge two networks and loopback addresses
are not unique anymore ;-)
Regarding RIRs we haven't had real problems using public address space.
As mentioned by Christopher: talk to them is the solution. Of course
they will ask you if you can't use private address space - that's their
Management in VPN networks: plan for address collisions. Anything else
but (your own) public addresses can be used by the customers.
198.18.0.0/15 doesn't help you for all times ("oh, we use that for our
extranet as all partners had 10.x.x.x in use like us"). Maybe using a
separate management VRF on the CPE and DLCI/PVC/VLAN on the CPE-PE link
is an option. Or use management address ranges in all 3 RFC1918
networks to lower the probability of collisions - often customers use
only 1 or 2 address ranges. I've also seen NAT on the provider end of
the management DLCI/PVC together with management address ranges per
On Friday, June 6, 2003, at 06:05 PM, m.rapoport at completel.fr wrote:
> I was wondering what are the choices made by Service Providers on the
> loopback addressing.
> 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
> Core routers.
> However, considering that these loopbacks are only used for routing
> protocols (OSPF,BGP, LDP)
> and for network management (SNMP, telnet, ...) and that these
> don't need to visible from public Internet
> (not seen in traceroute, not seen on Internet BGP announces ...) I am
> considering to
> use private RFC1918 for a new Backbone deployment.
> N.B. : Assumption is that e-BGP sessions with Internet peers are done
> 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
> 2) Loopback on CPE routers of the MPLS VPN customers.
> For this case, the issue is to assign the adresses in a global range
> all the CPE of
> all the VPN customers.
> In fact, all these loopback will need to be part of the Network
> 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
> Addresses unicity among all the customers is required due to the
> Management VPN common
> to all the customers.
> Using public address guarantee unicity, but will create issues with
> 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
> lab testing.
> 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 ...
Marc Binderberger <marc at sniff.de> Powered by *BSD ;-)
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