IP Addresses and Services Configuration Guide for Cisco 8000 Series Routers, IOS XR Releases

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IP Addresses and Services Configuration Guide for Cisco 8000 Series Routers, IOS XR Releases

DHCPv6 relay over BVI for IANA address allocation

Updated: August 12, 2026

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This topic describes DHCPv6 relay over a Bridge Virtual Interface (BVI) for Internet Assigned Numbers Authority (IANA) address allocation on the Cisco 8000 Series Router, which lets a DHCPv6 relay agent act as a stateful relay and maintain client bindings and route entries.

DHCPv6 relay agents relay all packets that are coming from DHCPv6 clients over the access-interfaces toward external DHCPv6 servers. DHCPv6 relay agents request IP addresses (::/128) through IANA allocation for the DHCPv6 clients. DHCPv6 relay agents also receive response packets from the DHCPv6 servers and forward the packets toward DHCPv6 clients over BVI interfaces. DHCPv6 relay agents act as stateless, by default, for DHCPv6 clients. DHCPv6 clients do not maintain any DHCPv6 binding and respective route entry for the allocated IP addresses. You can enable a DHCPv6 client to get a particular IPv6 address assigned by the DHCPv6 server over a BVI through IANA address allocation. Therefore, the DHCPv6 relay agent acts as a stateful relay agent and maintains DHCPv6 binding and respective route entry for the allocated IPv6 addresses.

Table 1. Feature History Table
Feature Name	Release	Description
DHCPv6 Relay Over BVI for IANA Address Allocation	Release 26.2.1	Introduced in this release on: Fixed Systems (8010 [ASIC: A100]) This feature is supported on: 8011-4G24Y4H-I 8011-32Y8L2H2FH 8011-12G12X4Y-A/D
DHCPv6 Relay Over BVI for IANA Address Allocation	Release 26.1.1	Introduced in this release on: Centralized Systems (8400 [ASIC: K100])(select variants only) This feature is now supported on Cisco 8404-SYS-D routers.

Restrictions for DHCPv6 relay over BVI for IANA address allocation

These restrictions apply to DHCPv6 relay over BVI for IANA address allocation:

You can configure up to 500 client sessions over a BVI interface for DHCP relay.
You can configure up to 8 DHCPv6 server addresses for each DHCPv6 relay profile.

Configure DHCPv6 relay over BVI for IANA address allocation

Procedure

Enter the interface configuration mode and configure a BVI interface.
Example:
```
Router# configure
Router(config)# interface BVI1
```

Assign an IPv6 address to the BVI interface.

Example:

Router(config-if)# ipv6 address 2001:db8::2/64
Router(config-if)# commit
Router(config-if)# exit

Route the L2 access interface to the L3 BVI interface of the relay agent.

Example:

Router(config)# l2vpn bridge group 1
Router(config-l2vpn-bg)# bridge-domain 1
Router(config-l2vpn-bg-bd)# interface hundredGigE 0/0/0/1.100
Router(config-l2vpn-bg-bd-ac)# commit
Router(config-l2vpn-bg-bd-ac)# exit
Router(config-l2vpn-bg-bd)# routed interface BVI1
Router(config-l2vpn-bg-bd)# exit
Router(config-l2vpn-bg)# exit
Router(config-l2vpn)# exit

Enter the DHCP IPv6 configuration mode and then create a DHCP IPv6 stateful relay profile.
Example:
```
Router(config)# dhcp ipv6
Router(config-dhcpv6)# profile RELAY1 relay
```

Attach the relay profile to a server address.

Example:

Router(config-dhcpv6-relay-profile)# helper-address vrf default 2001:DB8::1

Configure a stateful relay agent by enabling route allocation through IANA.

Example:

Router(config-dhcpv6-relay-profile)# iana-route-add
Router(config-dhcpv6-relay-profile)# exit

Attach the BVI interface to the DHCPv6 relay profile and commit the configuration.

Example:

Router(config-dhcpv6)# interface BVI1 relay profile RELAY1
Router(config-dhcpv6)# commit

Verify that more than one DHCP client is bridged over the BVI.

Example:

Router# show dhcp ipv6 relay binding
Summary:
Total number of clients: 500

IPv6 Address: 2000::418f/128 (BVI31)
    Client DUID: 000100015dcf28de001094003295
    MAC Address: 0010.9400.3295
    IAID: 0x0
    VRF: default
    Lifetime: 600 secs (00:10:00)
    Expiration: 533 secs (00:08:53)
    L2Intf AC: Bundle-Ether3.1
    SERG State: NONE
    SERG Intf State: SERG-NONE
IPv6 Address: 2000::4190/128 (BVI31)
Client DUID: 000100015dcf28de001094003296
MAC Address: 0010.9400.3296
IAID: 0x0
VRF: default
Lifetime: 600 secs (00:10:00)
Expiration: 531 secs (00:08:51)
L2Intf AC: Bundle-Ether3.1
SERG State: NONE
SERG Intf State: SERG-NONE
IPv6 Address: 2000::4191/128 (BVI31)
Client DUID: 000100015dcf28de001094003297
MAC Address: 0010.9400.3297
IAID: 0x0
VRF: default
Lifetime: 600 secs (00:10:00)
Expiration: 448 secs (00:07:28)
L2Intf AC: Bundle-Ether3.1
SERG State: NONE
SERG Intf State: SERG-NONE
IPv6 Address: 2000::4192/128 (BVI31)
Client DUID: 000100015dcf28de001094003298
MAC Address: 0010.9400.3298
IAID: 0x0
VRF: default
Lifetime: 600 secs (00:10:00)
Expiration: 439 secs (00:07:19)
L2Intf AC: Bundle-Ether3.1
SERG State: NONE
SERG Intf State: SERG-NONE

Verify that a unique IPv6 address is assigned to a client due to IANA allocation.

Example:

Router# show route ipv6
Mon Oct 21 06:16:43.617 UTC
Codes: C - connected, S - static, R - RIP, B - BGP, (>) - Diversion path
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - ISIS, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, su - IS-IS summary null, * - candidate default
U - per-user static route, o - ODR, L - local, G - DAGR, l - LISP
A - access/subscriber, a - Application route
M - mobile route, r - RPL, t - Traffic Engineering, (!) - FRR Backup path
Gateway of last resort is not set
A 2000::/64
[1/0] via fe80::1, 00:00:37, BVI700
A 2000::1/128
[1/0] via fe80::210:94ff:fe00:8, 00:00:12, BVI700
C 2007:3019::/64 is directly connected,
00:00:37, Loopback1
L 2007:3019::1/128 is directly connected,
00:00:37, Loopback1
C 7001:6018::/64 is directly connected,
00:00:37, BVI700
L 7001:6018::1/128 is directly connected,
00:00:37, BVI700
C 7001:6019::/64 is directly connected,
00:00:37, TenGigE0/0/0/2.2
L 7001:6019::1/128 is directly connected,
00:00:37, TenGigE0/0/0/2.2

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