Juniper JUNOS OS 10.4 - RELEASE NOTES REV 6 Release Note page 35

Copyright © 2011, Juniper Networks, Inc.
New Features in Junos OS Release 10.4 for M Series, MX Series, and T Series Routers
Per-interface DHCP tracing operations (MX Series routers)—In addition to the existing
global DHCP tracing operation, you can now trace DHCP operations for a specific
interface or a range of interfaces.
Configuring interface-based tracing is a two-step procedure. First configure the tracing
options that you want to use, such as the file used for the trace operation and the trace
flags. In the second step, enable the tracing operation on the specific interface or range
of interfaces.
To configure the per-interface tracing options, use the
statement at the
[edit system services dhcp-local-server]
local server or at the [edit forwarding-options dhcp-relay]
relay agent.
To enable tracing on an interface or interface range, use the
[edit system services dhcp-local-server group group-name interface interface-name]
hierarchy level for the DHCP local server, or the
group group-name interface interface-name]
You can also enable tracing for DHCPv6 at the
dhcpv6 group group-name interface interface-name]
[Subscriber Access]
Automatic binding of stray DHCP requests (MX Series routers)—The default behavior
has changed for handling DHCP requests that are received but which have no entry in
the database (stray requests). Beginning with Junos OS Release 10.4, automatic binding
of stray requests is enabled by default. In Junos OS Release 10.3 and earlier releases,
automatic binding of stray requests is disabled by default.
By default, DHCP relay and DHCP relay proxy now attempt to bind the requesting client
by creating a database entry and forwarding the request to the DHCP server. If the
server responds with an ACK, the client is bound and the ACK is forwarded to the client.
If the server responds with a NAK, the database entry is deleted and the NAK is
forwarded to the client. This behavior occurs regardless of whether authentication is
configured.
In Junos OS Release 10.3 and earlier releases, DHCP relay drops stray requests and
forwards a NAK to the client when authentication is configured. Otherwise, DHCP relay
attempts to bind the requesting client. In those releases, DHCP relay proxy always
drops stray requests and forwards a NAK to the client, regardless of the authentication
configuration.
You can override the new default configuration to cause DHCP relay and DHCP relay
proxy to drop all stray requests instead of attempting to bind the clients. To disable
automatic binding behavior globally, include the
[edit forwarding-options dhcp-relay overrides]
binding behavior for a group, include the statement at the
dhcp-relay overrides group group-name]
behavior for a specific interface in a group, include the statement at the
forwarding-options dhcp-relay overrides group group-name interface interface-name]
hierarchy level.
interface-traceoptions
hierarchy level for the DHCP
hierarchy level for the DHCP
trace
[edit forwarding-options dhcp-relay
hierarchy level for the DHCP relay agent.
[edit system services dhcp-local-server
hierarchy level.
no-bind-on-request
hierarchy level. To disable automatic
[edit forwarding-options
hierarchy level. To disable automatic binding
statement at the
statement at the
[edit
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