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Re: Best Practices for Loopback addressing (Core routers & VPN CPE)
- From: Marc Binderberger
- Date: Sun Jun 08 12:49:49 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, email@example.com wrote:
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
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
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
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
If you consider your adressing policy as touchy topic in terms of
security, don't hesitate to reply in private ...
Marc Binderberger <firstname.lastname@example.org> Powered by *BSD ;-)