Re: source addr. for icmp if link-local-only on interface

Is this what you mean? see output below for my test of what i think you are
talking about...

it appears to pick the lowest IPv6 address for this, dont know about the RFC
or Cisco implentation where this rule is coming from...

the ipv4 "rule" was it used the ip address closet to the destination to
source this packet when you did the ping from the router, unless of course
you specify the source interface

R1(config-if)#do ping 2002:2222::2 r 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 2002:2222::2, timeout is 2 seconds:
.
Success rate is 0 percent (0/1)

R2#debug ipv6 packet access-list ICMP detail
IPv6 unicast packet debugging is on (detailed) for access list ICMP
R2#
*Mar 1 00:20:58.635: IPV6: source 2444:4444::4 (Serial0/0)
*Mar 1 00:20:58.635: dest 2002:2222::2
*Mar 1 00:20:58.635: traffic class 0, flow 0x0, len 100+4, prot 58,
hops 64, forward to ulp
*Mar 1 00:20:58.639: IPV6: source 2002:2222::2 (local)
*Mar 1 00:20:58.639: dest 2444:4444::4
*Mar 1 00:20:58.639: traffic class 0, flow 0x0, len 100+4, prot 58,
hops 64, Route not found

R1(config-if)#int loop4
R1(config-if)#shut
R1(config-if)#int loop4
*Mar 1 00:22:15.835: %LINK-5-CHANGED: Interface Loopback4, changed state to
administratively down
*Mar 1 00:22:16.835: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Loopback4, changed state to down
R1(config-if)#do ping 2002:2222::2 r 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 2002:2222::2, timeout is 2 seconds:
.
Success rate is 0 percent (0/1)

R2#
*Mar 1 00:22:18.999: IPV6: source 2555:5555::5 (Serial0/0)
*Mar 1 00:22:19.003: dest 2002:2222::2
*Mar 1 00:22:19.003: traffic class 0, flow 0x0, len 100+4, prot 58,
hops 64, forward to ulp
*Mar 1 00:22:19.003: IPV6: source 2002:2222::2 (local)
*Mar 1 00:22:19.003: dest 2555:5555::5
*Mar 1 00:22:19.003: traffic class 0, flow 0x0, len 100+4, prot 58,
hops 64, Route not found

R1(config-if)#no shut
R1(config-if)#int f0/0
R1(config-if)#no shut
R1(config-if)#
*Mar 1 00:23:01.319: %LINK-3-UPDOWN: Interface Loopback4, changed state to
up
*Mar 1 00:23:02.319: %LINEPROTO-5-UPDOWN: Line protocol on Interface
Loopback4, changed state to up
R1(config-if)#
*Mar 1 00:23:04.787: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed
state to up
*Mar 1 00:23:05.787: %LINEPROTO-5-UPDOWN: Line protocol on Interface
FastEthernet0/0, changed state to up
R1(config-if)#do ping 2002:2222::2 r 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 2002:2222::2, timeout is 2 seconds:
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 44/44/44 ms
R2#
*Mar 1 00:23:19.951: IPv6: Sending on Serial0/0
*Mar 1 00:23:20.303: IPV6: source 2001:1111::1 (Serial0/0)
*Mar 1 00:23:20.303: dest 2002:2222::2
*Mar 1 00:23:20.303: traffic class 0, flow 0x0, len 100+4, prot 58,
hops 64, forward to ulp
*Mar 1 00:23:20.307: IPv6: nexthop FE80::1,
*Mar 1 00:23:20.307: IPV6: source 2002:2222::2 (local)
*Mar 1 00:23:20.307: dest 2001:1111::1 (Serial0/0)
*Mar 1 00:23:20.307: traffic class 0, flow 0x0, len 100+4, prot 58,
hops 64, originating

ROUTER CONFIGS for TEST:

hostname R1
!
ipv6 unicast-routing
!
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback4
 no ip address
 ipv6 address 2444:4444::4/64
!
interface Loopback5
 no ip address
 ipv6 address 2555:5555::5/64
!
interface Loopback6
 no ip address
 ipv6 address 2666:6666::6/64
!
interface FastEthernet0/0
 no ip address
 shutdown
 duplex auto
 speed auto
 ipv6 address 2001:1111::1/64
 ipv6 ospf 1 area 1
!
interface Serial0/0
 no ip address
 ipv6 address FE80::1 link-local
 ipv6 ospf 1 area 0
 clock rate 2000000
!
ipv6 router ospf 1

hostname R2
!
ipv6 unicast-routing
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 ipv6 address 2002:2222::2/64
 ipv6 ospf 1 area 2
!
interface Serial0/0
 no ip address
 ipv6 address FE80::2 link-local
 ipv6 ospf 1 area 0
 clock rate 2000000
!
ipv6 router ospf 1
!
ipv6 access-list ICMP
 permit icmp any any

 --
Garry L. Baker

"With sufficient thrust, pigs fly just fine..." - RFC 1925

On Fri, Sep 2, 2011 at 11:58 AM, Roger Pfaeffli <rpf23543_at_gmail.com> wrote:

> Hi group,
>
> On a router, if I have on a WAN link just the ipv6 link local address
> ('cause this is enough for routing) and I execute a v6ping to a global
> scoped address somewhere in this WAN, my router chooses a global
> scoped address, borrowed from another interface of my router. That's
> at least what I've tested.
> How is this "borrowed" address chosen and where is this specified? I
> could not find an rfc describing exactly this. I guess this is vendor
> specific, if so, is there a documentation from Cisco explaining this?
>
> regards
>
> Roger #23543
>
>
> Blogs and organic groups at http://www.ccie.net
>
> _______________________________________________________________________
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Received on Fri Sep 02 2011 - 14:03:27 ART