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CE Router not picking up IPv6 Prefix-Delegation and inserting a static route...


So I have a series of customers that all have various manufacturers of dual stack home routers.  They are picking up both IPv4 and IPv6 addresses from me as well as a PD (prefix delegation) for their internal network (typically a /64, sometimes a /56).  I am using the ISC KEA DHCPv4/v6 server on my back end.


I've tested the DHCP server and its correctly analyzing the packet requests and sending both an IPv6 address and IPv6 PD (as well as other information) back to the requesting router.  The CE-Router (currently a Cisco 7301 IOS 15.2(4)M11 [c7301-adventerprisek9-mz.152-4.M11.bin]) is giving the correct information to the client however the router is NOT inserting a static route into its routing table for the allocated PD.  Same behavior both with and without IPv6 traffic-filters 


Note: A-flag off w/prefix, M-flag on, O-flag off, 


Config on the CE-Router



service dhcp


ipv6 general-prefix tower-sjc 2604:xxxx:xxxx:1::/64

ipv6 unicast-routing
ipv6 cef
ipv6 dhcp iana-route-add


interface GigabitEthernet0/1.121
description ::Tower CE (v121)
encapsulation dot1Q 121
ip dhcp relay information option-insert
ip dhcp relay information check-reply
ip address
ip access-group CE-inbound in
ip access-group CE-outbound out
ip helper-address
standby version 2
standby 121 ip
standby 121 priority 105
standby 121 preempt
standby 121 track 2 decrement 10

! This is our HSRP link-local address on this interface
standby 221 ipv6 FE80::121:1
standby 221 priority 105
standby 221 preempt delay minimum 30
standby 221 track 2 decrement 10
ip ospf cost 10

! Set link-local to indicate VLAN and router number
ipv6 address FE80::121:2 link-local
ipv6 address tower-sjc ::1/64
ipv6 enable

! Turn off the A flag (but still advertise the prefix)
ipv6 nd prefix 2604:xxxx:xxxx:1::/64 no-advertise

! Turn on the M flag (for managed configuration via stateful DHCPv6)
ipv6 nd managed-config-flag

! Relay to stateful DHCPv6 server
ipv6 dhcp relay destination 2604:xxxx:xxxx:xxxx::FEED:200
ipv6 traffic-filter CE-IPv6-inbound in
ipv6 traffic-filter CE-IPv6-outbound out
ipv6 ospf 101 area 0
ipv6 ospf priority 0
no keepalive


So I've been experimenting with this and the "ipv6 dhcp iana-route-add" statement is supposed to work based on all the documentation I could find (which then allows for propigation in your IGP) however experimenting and testing shows that its not in fact working.  Unless there is an error in the configuration I'd say this is a broken command  from Cisco IOS

2 Replies 2

Flavio Miranda

Hi @mdella000


I have found this warn here:

" PE-router running IOS release 15.0(1)M did not insert the required static route when working as a DHCPv6 relay. DHCPv6 server functionality worked as expected."

 Although your version is newer I also saw people complaining about his problem in newer versions. However, did not find on which version this is expected to be fully supported.


-If I helped you somehow, please, rate it as useful.-


Not sure how this would be helpful information as it doesn't give me any new information. I already had that for the 15.0 series (I'm running 15.2 as stated originally) so I have no new references to validate against. Also it appears no one from Cisco IPv6 group actually reads these things either.

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