Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - RELEASE NOTES 2010-11-09 Release Note page 29

Copyright © 2010, Juniper Networks, Inc.
When a bound DHCP client on a dynamic subscriber interface extends its IP address

lease by restarting the DHCP discovery process on its primary IP interface instead of
by initiating the DHCP renewal process on its dynamic subscriber interface, the
default behavior of the DHCP external server application to preserve the client's
dynamic subscriber interface was changed in the following JunosE releases to delete
and re-create the client's dynamic subscriber interface:
 Release 7.2.4p0-4 and all higher-numbered 7.2.x releases and patch releases
 Release 7.3.4 and all higher-numbered 7.3.x releases and patch releases
 Release 8.0.4 and all higher-numbered 8.0.x releases and patch releases
 Release 8.1.2 and all higher-numbered 8.1.x releases and patch releases
 Release 8.2.3 and all 8.2.3 patch releases
 Release 9.0.0 and all 9.0.0 patch releases
 Release 9.0.1 and all 9.0.1 patch releases
 Release 9.1.0 and all 9.1.0 patch releases
If you are upgrading the JunosE Software on the router from any of these releases,
you must explicitly issue the ip dhcp-external recreate-subscriber-interface
command to configure the router to continue to delete and re-create the DHCP
client's dynamic subscriber interface.
Informational Note:
The DHCP external server application is unsupported in JunosE
Release 8.2.1 and JunosE Release 8.2.2.
DHCP NAK packets are sent from a different VLAN than the one on which the renew

request is received on a router that is configured with dynamic VLANs, DHCP local
server, and automatically created dynamic subscriber interfaces. This behavior
occurs only after a link flap has taken place.
DHCP external server may not be able to bind all DHCP clients when all of the

following conditions exist:
 DHCP external server and either DHCP relay or relay proxy are configured in
separate virtual routers on an E320 router.
 The client-facing and server-facing interfaces for DHCP external server and
either DHCP relay or relay proxy are configured on the same ES2 4G LM.
 DHCP external server is configured to create dynamic subscriber interfaces.
When these three conditions exist simultaneously, the ES2 4G LM may not be able to
successfully process all DHCP packets. Although all clients may get bounded in
DHCP relay or relay proxy, some clients may not get bounded in DHCP external
server. (In a production environment it is highly unlikely for conditions 1 and 2 to exist
because stand-alone DHCP external server is normally configured for a DHCP relay in
a different chassis.)
Release 11.3.0
Known Behavior 21