Question about learning default route and on-link route through ND in IPv6 network

[angelyouyou]

There are four command lines related to generating default routes and direct routes (Cisco7200 15.2(4) M11). I want to know the relationship, differences, and processing behavior of these command lines:
1.ipv6 nd autoconfig prefix
2.ipv6 nd autoconfig default-router
3.ipv6 address autoconfig [default]
4.ipv6 nd route-owner

About how the default route is generated:
What is the relationship between ipv6 nd autoconfig default-router and ipv6 address autoconfig default?
As long as you configure ipv6 enable on the interface, you can generate a default route even if you do not configure these two command lines.

About how to generate on-link routes:
ipv6 nd autoconfig prefix can generate an on-link route based on L tags.
ipv6 address autoconfig can generate an address based on the A tag to generate an on-link route.

About the tag of the direct route:
By default, the Cisco 7200 is enabled with the ipv6 nd route-owner, and the 'NDp' route is generated according to the RA. The default route with 'ND' flag is generated, This flag does not match the description of the document below.

"

Command Default

The status of Neighbor Discovery-learned routes is "Static."

"

Experimental topology(both client1 and client2 has the same default (ND) and on-link (NDp) routes):
Router----Client1(ipv6 address autoconfig)

|

|

Client2(ipv6 nd autoconfig prefix)

Device version (both router and client):
Client#show version
Cisco IOS Software, 7200 Software (C7200-ADVENTERPRISEK9_SNA-M), Version 15.2(4)M11, RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2016 by Cisco Systems, Inc.
Compiled Sun 16-Oct-16 07:53 by prod_rel_team

Router side configuration:
!
Interface GigabitEthernet1/0
 no ip address
 negotiation auto
 ipv6 address FE80::1 link-local
 ipv6 address 2001::1/64
 ipv6 enable
 ipv6 nd ra interval 10
!

Client1 side configuration:
!
Interface GigabitEthernet1/0
 no ip address
 negotiation auto
 ipv6 address FE80::1 link-local
 ipv6 address 2001::1/64
 ipv6 enable
 ipv6 nd ra interval 10
!

Client1#show ipv6 route

IPv6 Routing Table - default - 4 entries

Codes: C - Connected, L - Local, S - Static, U - Per-user Static route

B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP

H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea

IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO

ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect

O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2

ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP

ND ::/0 [2/0]

via FE80::1, GigabitEthernet1/0

NDp 2001::/64 [2/0]

via GigabitEthernet1/0, directly connected

L 2001::C803:51FF:FEF8:1C/128 [0/0]

via GigabitEthernet1/0, receive

L FF00::/8 [0/0]

via Null0, receive

Client2 side configuration:

!

interface GigabitEthernet1/0

no ip address

negotiation auto

ipv6 enable

ipv6 nd autoconfig prefix

!

Client2#show ipv6 route

IPv6 Routing Table - default - 3 entries

Codes: C - Connected, L - Local, S - Static, U - Per-user Static route

B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP

H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea

IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO

ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect

O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2

ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP

ND ::/0 [2/0]

via FE80::1, GigabitEthernet1/0

NDp 2001::/64 [2/0]

via GigabitEthernet1/0, directly connected

L FF00::/8 [0/0]

via Null0, receive

After I config 'no ipv6 nd route-owner' on both clients(client1 and client2), only static default route left.

Client1#show ipv6 route
IPv6 Routing Table - default - 3 entries
Codes: C - Connected, L - Local, S - Static, U - Per-user Static route
B - BGP, HA - Home Agent, MR - Mobile Router, R - RIP
H - NHRP, I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
IS - ISIS summary, D - EIGRP, EX - EIGRP external, NM - NEMO
ND - ND Default, NDp - ND Prefix, DCE - Destination, NDr - Redirect
O - OSPF Intra, OI - OSPF Inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2, l - LISP
S ::/0 [2/0]
via FE80::1, GigabitEthernet1/0
L 2001::C803:51FF:FEF8:1C/128 [0/0]
via GigabitEthernet1/0, receive
L FF00::/8 [0/0]
via Null0, receive

[Harold Ritter]

Hi Angel,

> 1.ipv6 nd autoconfig prefix

This command is not to generate, but rather to install the on-link prefixes from the received router advertisement (RA).

> 2.ipv6 nd autoconfig default-router

This command is not to generate, but rather install the default route from the received router advertisement (RA).
> 3.ipv6 address autoconfig [default]

This command is to enable the SLAAC behavior on the local interface.

> 4.ipv6 nd route-owner

This command set ND as the owner of the installed routes. The owner is static by default. The default varies depending on the IOS version.

Regards,

[angelyouyou]

Thanks for your reply!

> 1.ipv6 nd autoconfig prefix

This command is not to generate, but rather to install the on-link prefixes from the received router advertisement (RA).

--------->

I know this command is not to generate. Regardless of whether the command line is enabled or not, a connected route is generated after receiving the ND RA.

I want to know what is the reason for this? Not quite consistent with the introduction of the command line.

> 2.ipv6 nd autoconfig default-router

This command is not to generate, but rather install the default route from the received router advertisement (RA).

--------->

I know this command is not to generate. Regardless of whether the command line is enabled or not, a default route is generated after receiving the ND RA.

I want to know what is the reason for this? Not quite consistent with the introduction of the command line.

> 3.ipv6 address autoconfig [default]

This command is to enable the SLAAC behavior on the local interface.

--------->

Regardless of whether the default key word is specified or not, a default route is generated after receiving the ND RA.

I want to know what is the reason for this? Not quite consistent with the introduction of the command line.

Another question???????

5. Topic about default route
(1)Generating a  defaut route

What is the relationship and difference between this command line that specifies the default keyword and the 'ipv6 nd autoconfig default router' command line?

(2)Load  sharing about default route
When receiving ND RA packets from two different routers, will two default routes for load sharing be generated (if the priorities in the ND RA are the same)? From the actual test, it seems that only one default route will be generated according to the rank. How is the rank priority determined?

6.ipv6 address autoconfig [default]
Why is this default keyword only specified on one interface at the same time?