3.6. Triple Play DHCP Command Reference

This command creates a text description stored in the configuration file for a configuration context.

The description command associates a text string with a configuration context to help identify the content in the configuration file.

The no form of the command removes the string from the configuration.

This command administratively disables an entity. When disabled, an entity does not change, reset, or remove any configuration settings or statistics.

The operational state of the entity is disabled as well as the operational state of any entities contained within. Many objects must be shut down before they may be deleted.

The no form of the command places the entity into an administratively enabled state.

This command enables the context to configure DHCP parameters.

This command configures the different DHCPv6 applications to send the NoAddrsAvail Status-Code in DHCPv6 Advertise messages at the global DHCP message level.

By default, all applications send the NoAddrsAvail Status-Code in DHCPv6 Advertise messages at the IA_NA Option level.

Different applications for which NoAddrsAvail Status-Code in DHCPv6 Advertise messages can be configured at the global DHCP message level.

The only valid combination in current SR OS is adv-noaddrs-global esm-relay server.

The no form of the command reverts to the default.

This command creates a configuration context for the specified DHCP filter policy if it does not exist and enables the context to configure the specified DHCP filter policy.

This command creates a configuration context for the specified DHCPv6 filter policy if it does not exist and enables the context to configure the specified DHCPv6 filter policy.

The no form of this command reverts to the default.

This command specifies the default action when no entries match.

The no form of this command reverts to the default.

This command configures DHCP filter entries.

The no form of the command removes the entry from the configuration.

This command specifies the action to take on DHCP host creation when the filter entry matches.

The no form of the command reverts to the default wherein the host creation proceeds as normal.

This command configures the match criteria for the DHCP filter policy entry.

The no form of the command reverts to the default.

This command instantiates a local DHCP server. A local DHCP server can serve multiple interfaces but is limited to the routing context it was which it was created.

The no form of the command reverts to the default.

If enabled, the local DHCPv6 server will handle and reply to lease query messages.

The no form of the command disables lease query support.

This command enables the context to configure failover parameters.

With this flag enabled, the remote IP address/prefix can be taken over immediately upon entering the PARTNER-DOWN state of the intercommunication link, without having to wait for the Maximum Client Lead Time (MCLT) to expire. By setting this flag, the lease times of the existing DHCP clients, while the intercommunication link is in the PARTNER-DOWN state, will still be reduced to the MCLT over time and all new lease times will be set to MCLT. This behavior remains the same as originally intended for MCLT.

Some deployments require that the remote IP address/prefix range starts delegating new IP addresses/prefixes upon the failure of the intercommunication link, without waiting for the intercommunication link to transition from the COMM-INT state into the PARTNER-DOWN state and the MCLT to expire while in PARTNER-DOWN state.

This can be achieved by enabling the ignore-mclt-on-takeover flag and by configuring the partner-down-delay to 0.

Enabling this functionality must be exercised with caution. One needs to keep in mind that the partner-down-delay and MCLT timers were originally introduced to prevent IP address duplication in cases where DHCP redundant nodes transition out-of-sync due to the failure of intercommunication link. These timers (partner-down-delay and MCLT) would ensure that during their duration, the new IP addresses/prefixes are delegated only from one node, the one with local IP address-range/prefix. The drawback is of course that the new IP address delegation is delayed and thus service is impacted.

But if one could ensure that the intercommunication link is always available, then the DHCP nodes would stay in sync and the two timers would not be needed. This is why it is of utmost importance that in this mode of operation, the intercommunication link is well protected by providing multiple paths between the two DHCP nodes. The only event that should cause intercommunication link to fail is the entire nodal failure. This failure is acceptable since in this case only one DHCP node is available to provide new IP addresses/prefixes.

The no form of the command reverts to the default.

The maximum-client-lead-time (MCLT) is the maximum time that a DHCP server can extend client’s lease time beyond the lease time currently known by the DHCP partner node. In dual-homed environment, the initial lease time for all DHCP clients is by default restricted to MCLT. Consecutive DHCP renews are allowed to extend the lease time beyond the MCLT.

The MCLT is a safeguard against IP address/prefix duplication in cases of a lease synchronization failure when local-remote failover model is deployed

Once the intercommunication link failure between the redundant DHCP servers is detected, the DHCP IP address range configured as remote will not be allowed to start delegating new leases until the MCLT + partner-down-delay intervals expire. This is to ensure that the new lease that was delegated from the ‘local’ IP address-range/prefix on one node, but was never synchronized due to the intercommunication link failure, will expire before the same IP address/prefix is allocated from the remote IP address-range/prefix on the other node.

However, the already existing (and synchronized) lease times can be renewed from the remote IP address range at any time, regardless of the state of the intercommunication link (operational or failed).

Lease synchronization failure can be caused either by a node failure, or a failure of the link over which the DHCP leases are synchronized (intercommunication link). Synchronization failure detection can take up to 3 seconds.

During the failure, the DHCP lease time for the new clients will be restricted to MCLT while for the existing clients the lease time will over time (by consecutive DHCP renews) be gradually reduced to the MCLT.

The no form of the command reverts to the default.

Since the DHCP lease synchronization failure can be caused by the failure of the intercommunication link (and not necessary the entire node), there is a possibility the redundant DHCP servers become isolated in the network. In other words, they can serve DHCP clients but they cannot synchronize the lease. This can lead to duplicate assignment of IP addresses, since the servers have configured overlapping IP address ranges but they are not aware of each other’s leases.

The purpose of the partner-down-delay is to prevent the IP lease duplication during the intercommunication link failure by not allowing new IP addresses to be assigned from the remote IP address range. This timer is intended to provide the operator with enough time to remedy the failed situation and to avoid duplication of IP addresses/prefixes during the failure.

During the partner-down-delay time, the prefix designated as remote will be eligible only for renewals of the existing DHCP leases that have been synchronized by the peering node. Only after the sum of the partner-down-delay and the maximum-client-lead-time will the prefix designated as remote be eligible for delegation of the new DHCP leases. When this occurs, we say that the remote IP address range has been taken over.

It is possible to expedite the takeover of a remote IP address range so that the new IP leases can start being delegated from that range shortly after the intercommunication failure is detected. This can be achieved by configuring the partner-down-delay timer to 0 seconds, along with enabling the ignore-mclt-on-takeover CLI flag. Caution must be taken before enabling this functionality. It is safe to bypass safety timers (partner-down-delay + MCLT) only in cases where the operator is certain that the intercommunication between the nodes has failed due to the entire node failure and not due to the intercommunication (MCS) link failure. Failed intercommunication due to the nodal failure would ensure that only one node is present in the network for IP address delegation (as opposed to two isolated nodes with overlapping IP address ranges where address duplication can occur). For this reason, the operator must ensure that there are redundant paths between the nodes to ensure uninterrupted synchronization of DHCP leases.

In access-driven mode of operation, partner-down-delay has no effect.

The no form of the command reverts to the default.

DHCP leases can be synchronized per DHCP server of DHCP pool. The pair of synchronizing servers or pools is identified by a tag. The synchronization information is carried over the Multi-Chassis Synchronization (MCS) link between the two peers. MCS link is a logical link (IP, or MPLS).

MCS runs over TCP, port 45067 and it is using either data traffic or keepalives to detect failure on the communication link between the two nodes. In the absence of any MCS data traffic for more than 0.5sec, MCS will send its own keepalive to the peer. If a reply is not received within three sec, MCS will declare its operation state as DOWN and the DB Sync state as out-of-sync. MCS will consequently notify its clients (DHCP Server being one of them) of this. It can take up to three seconds before the DHCP client realizes that the inter-chassis communication link has failed.

The inter-chassis communication link failure does not necessarily assume the same failed fate for the access links. The two redundant nodes can become isolated from each other in the network. This would occur in cases where only the intercommunication (MCS) link fails. It is of utmost importance that this MCS link be highly redundant.

The no form of the command reverts to the default.

This command enables startup-wait-time during which each peer waits after the initialization process before assuming the active role for the prefix designated as local or access-driven. This is to avoid transient issues during the initialization process.

The startup-wait-time should be configured to an interval in which, after boot, both nodes can set up an MCS TCP link and start MCS. The timer is restarted each time the server downloads a lease from the MCS database and stops when the last state record from the peer is synchronized. The next state is (PRE-)NORMAL, unless the timer times out or is forced to stop via a new tools command (tools perform router dhcp or dhcp6 local-dhcp-server server-name [pool] failover abort-startup-wait), in which case the local DHCP server will transition immediately to the COMMUNICATIONS-INTERRUPTED state.

This command enables the sending of sending forcerenew messages.

The no form of the command disables the sending of forcerenew messages.

This command enables the Rapid Commit Option.

The no form of the command disables the Rapid Commit Option.

If enabled, this command enables the behavior where unique /64 prefix is allocated per interface-id, and all clients having the same interface-id get an address allocated out of this /64 prefix. This is relevant for bridged clients behind the same local-loop (and same SAP), where sharing the same prefix allows communication between bridged clients behind the same local-loop to stay local. For SLAAC based assignment, downstream neighbor-discovery is automatically enabled to resolve the assigned address.

The no form of the command reverts to the default.

This command configures the time to remember this lease and is applicable for unsolicited release conditions such as lease timeout if parameter lease-hold-time-for is set to the default value no solicited-release and is additionally applicable for normal solicited releases from DHCP clients if the lease-hold-time-for parameter is set to solicited-release.

The no form of the command reverts to the default.

This command enables the context to configure lease-hold-time-for parameters which defines additional types of lease or triggers that cause system to hold up leases.

The no form of the command reverts to the default.

This command enables the server to hold up the lease of local IPsec clients.

The no form of the command disables the ability of the server to hold up the lease of local IPSec clients.

This command enables the server to hold up a lease even in case of solicited release; for example, when the server receives a normal DHCP release message.

The no form of the command disables the ability of the server to hold up a lease when a solicited release is received.

This command configures a DHCP address pool on the router.

The no form of the command removes the pool name from the configuration.

This command configures the delegated prefix length that will be used if the DHCPv6 client does not specify a prefix length hint.

The DHCPv6 client prefix length hint is limited by the range specified by the minimum and maximum parameters. If the hint is smaller than the minimum, the allocated prefix length will be equal to the minimum length. If the hint is larger than the maximum, the allocated prefix length will be equal to the maximum length.

The no form of the command reverts to the default.

This command defines a prefix that to be excluded from available prefix in the pool. The typical use case is to exclude the interface address.

The no form of the command removes the prefix that is to be excluded from available prefix in the pool.

This command configures the maximum lease time.

The no form of the command reverts to the default.

This command configures the minimum lease time.

The no form of the command reverts to the default.

This command specifies the desired minimum number of free addresses in this pool.

The no form of the command reverts to the default.

With this command, if the local DHCPv4 server receives a DHCP request with option 50 (means client try to request a previous allocated message as described in section 3.2 of RFC 2131, Dynamic Host Configuration Protocol) and the address allocation algorithm ends up using a pool and the address in option50 is not in pool, then system will return a DHCP NAK, otherwise system just drop the DHCP packet.

The no form of the command reverts to the default.

This command configures the time interval during which a DHCP offer is valid.

The no form of the command reverts to the default.

This command enables the context to configure pool options. The options defined here can be overruled by defining the same option in the local user database.

This command configures specific DHCP options. The options defined here can overrule options in the local user database.

The no form of the removes the custom option parameters from the configuration.

This command configures the IP address of the DNS server.

The no form of the command removes the IP address from the DNS server configuration.

This command configures IPv6 DNS server addresses that can be used for name resolution

The no form of the command removes the IPv6 address from the dns-server configuration.

This command configures the default domain for a DHCP client that the router uses to complete unqualified host names (without a dotted-decimal domain name).

The no form of the command removes the name from the configuration.

This command configures the time the client transitions to a rebinding state.

The no form of the command removes the time from the configuration.

This command configures the time the client transitions to a renew state.

The no form of the command removes the time from the configuration.

This command configures the amount of time that the DHCP server grants to the DHCP client permission to use a particular IP address.

The no form of the command removes the lease time parameters from the configuration.

This command configures up to four Network Basic Input/Output System (NetBIOS) name server IP addresses.

The no form of the command removes the IP address from the netbios-name-server configuration.

This command configures the Network Basic Input/Output System (NetBIOS) node type.

The no form of the command removes the netbios node type parameters from the configuration.

This command configures MSAP authentication defaults.

This command configures the group interface.

The no form of the command removes the group interface parameters from the configuration.

This command configures the MSAP policy.

The no form of the command removes the MSAP policy name from the configuration.

This command sets default service for all subscribers created based on trigger packets received on the given capture SAP in case the corresponding VSA is not included in the RADIUS authentication response. This command is applicable to capture SAP only.

The no form of the command reverts to the default.

This command sets the retail-service ID for a given subscriber host.

The no form of the command reverts to the default.

This command allocates a prefix to a pool from which Prefix Delegation prefixes and or wan addresses can be assigned.

The no form of the command removes the prefix parameters from the configuration.

This command enables the context to configure pool level thresholds.

This command creates a threshold for a given prefix length on the pool level. Up to 128 thresholds could be created. For example, with minimum-free prefix-length 64, then the usage of /64 prefix in the pool is counted.

There are two types of thresholds that could be defined at the pool level:

Configuration of this command also enables the system stats collection for configure prefix length, which could be displayed via the show router router-id dhcp6 local-dhcp-server d6 pool-threshold-stats command.

The no form of the command removes the prefix-length from the configuration.

This command enables the system to send out warnings when the prefix with the configured length is no long available in the pool.

The no form of the command disables the warnings.

This command enables the system to send out a warning when the prefix with a configured length is no long available in the provisioned prefix.

For example:

With the above configuration, the system will send out a warning when there is no available /64 that can be allocated out of 2001:0:0:ffe0::/50.

The no form of the command disables the warnings.

This command specifies a percentage based threshold which represent the minimal available percentage of the prefix with configured length in the pool. The system will send out a warning if the actual percentage is lower than the configured percentage.

The no form of the command removes the percentage from the configuration.

This command configures a percentage-based or number-based threshold which represents the minimal available percentage or number of the prefix with a configured length in the provisioned prefix. The system will send out a warning if the actual percentage or number is lower than the configured threshold.

For example:

With the above configuration, the system will send a warning when the number of available /64 in prefix 2001:0:0:ffe0::/50 is less than 3.

The no form of the command removes the command parameters from the configuration.

This command enables the context to configure DHCP options to send to the client.

This command specifies local user database for PPP PAP/CHAP access.

With this configuration, system will access the specified DB again during PPP PAP/CHAP phase.

This configuration only becomes effective when system is accessing parent DB during PPPoE discovery phase.

The no form of the command removes the name from the configuration.

This command configures specific DHCP options. The options defined here can overrule options in the local user database.

The no form of the removes the option from the configuration.

This command configures DHCPv4 options via LUDB that will be passed in all DHCP messages to the client. The options will be blindly appended to any options already present in the DHCP message. In other words, there is no intelligent merging of the options where overlapping options from different sources are further evaluated to determine whether only one option or multiple options should be returned to the client.

Multiple DHCP options can be configured at the same time although each option requires its own option statement. Those options are equivalent to RADIUS VSAs Alc-ToCLient-Dhcp4-Options.

DHCPv4 options can be provided via DHCPv4 server in the relay case. In addition, DHCPv4 options provided via LUDB or RADIUS can be supplied and consequently appended to the already existing options. In case that DHCPv4 options are provided simultaneously via LUDB and RADIUS, the RADIUS as a source of DHCPv4 option will be blocked and the options supplied via LUDB will be passed to the client. This is valid for the relay and proxy case.

Any DHCP option may be encoded in the option statement. An example of the option statement for DHCPv4 default-gateway is given below:

option 3 192.168.1.254

DHCPv4 options may be fixed length or variable length. They are appended at the end of DHCPv4 messages. All options begin with a tag octet, which uniquely identifies the option. Fixed-length options without data consist of only a tag octet. Only options 0 and 255 are fixed length. All other options are variable-length.

The no form of the removes the option from the configuration.

This command creates a subnet of IP addresses to be served from the pool. The subnet cannot include any addresses that were assigned to subscribers without those addresses specifically excluded. When the subnet is created no IP addresses are made available until a range is defined.

The no form of the removes the subnet parameters from the configuration.

This command configures a range of IP addresses to be served from the pool. All IP addresses between the start and end IP addresses will be included (other than specific excluded addresses).

The no form of the command removes the address-range parameters from the configuration.

This command means no new leases can be assigned from this subnet and existing leases are cleaned up upon renew/rebind.

The no form of the command means the subnet is active and new leases can be assigned from it.

This command specifies a range of IP addresses that excluded from the pool of IP addresses in this subnet.

The no form of the removes the parameters from the configuration.

This command configures the maximum number of declined addresses allowed.

The no form of the reverts to the default.

This command configures the minimum number of free addresses in this subnet. If the actual number of free addresses in this subnet falls below this configured minimum, a notification is generated.

The no form of the reverts to the default.

This command configures the IP address of the default router for a DHCP client. Up to four IP addresses can be specified.

The no form of the command removes the address(es) from the configuration.

This command specifies the subnet-mask option to the client. The mask can either be defined (for supernetting) or taken from the pool address.

The no form of the command removes the address from the configuration.

This command enables the use of gi-address matching. If the gi-address flag is enabled, a pool can be used even if a subnets is not found. If the local-user-db-name is not used, the gi-address flag is used and addresses are handed out by GI only. If a user must be blocked from getting an address the server maps to a local user database and configures the user with no address.

A pool can include multiple subnets. Since the GI is shared by multiple subnets in a subscriber interface the pool may provide IP addresses from any of the subnets included when the GI is matched to any of its subnets. This allows a pool to be created that represents a sub-int.

The no form of the reverts to the default.

This command enables the use of the pool indicated by DHCP client. When enabled, the IP address pool to be used by this server is the pool is indicated by the vendor-specific sub-option 13 of the DHCP option 82. When disabled or if there is no sub-option 13 in the DHCP message, the pool selection falls back to the use-gi-address configuration.

The no form of the reverts to the default.

This command configures the user identification method for the DHCPv4 server.

The no form of the reverts to the default.

This command configures the keys for identification of the DHCPv6 lease being held in the lease-database (for configured period after lease timeout). Subscriber requesting a lease via DHCPv6 that matches an existing lease based on this configured key is handed the matched prefix or address. This allows address and prefix “stickiness” for DHCPv6 assigned prefixes (IA_NA or PD).

The no form of the reverts to the default.

This command configures the local pool selection for v6 address or prefix assignment to use the configured link-address under relay configuration. The selected pool will contain a prefix covering the link-address. The scope option defines the scope for the match. With scope subnet, the prefix or address selection is limited to the prefix in the pool that covers the link-address. With scope pool, all the prefixes in the selected pool are eligible for assignment.

The no form of the reverts to the default.

This command configures a local user database for authentication.

The no form of the command reverts to the default.

This command enables the context to configure DHCP6 parameters.

This command enables the context to configure DHCPv6 relay parameters for this interface.

This command enables DHCP relay and proxy-server for the configured client types.

The no form of the command reverts to the default.

This command enables matching Option 82 circuit ID on relayed DHCP packet matching.

For Routed CO, the group interface DHCP relay process is stateful. When packets are relayed to the server the virtual router ID, transaction ID, SAP ID, and client hardware MAC address of the relayed packet are tracked. When a response is received from the server the virtual router ID, transaction ID, and client HW MAC address must be matched to determine the SAP on which to send the packet out. In some cases, the virtual router ID, transaction ID, and client HW MAC address are not guaranteed to be unique.

When the match-circuit-id command is enabled this part of the key is used to guarantee correctness in the lookup. This is only needed when are dealing with an IP aware DSLAM that proxies the client HW mac address.

The no form of the command reverts to the default.

This command enables dynamic host lease state management for SAPs.

For VPLS, DHCP snooping must be explicitly enabled (using the snoop command) at all points where DHCP messages requiring snooping enter the VPLS instance (both from the DHCP server and from the subscribers). Lease state information is extracted from snooped DHCP ACK messages to populate lease state table entries for the MSAP.

The optional number-of-entries parameter is used to define the number lease state table entries allowed for an MSAP or IP interface. If number-of-entries is omitted, only a single entry is allowed. Once the maximum number of entries has been reached, subsequent lease state entries are not allowed and subsequent DHCP ACK messages are discarded.

The retained lease state information representing dynamic hosts may be used to:

The no form of the command disables dynamic host lease state management for the MSAP.

This command enables and disables dynamic host DHCPv4 lease state management for SAPs.

For VPLS, DHCP snooping must be explicitly enabled (using the snoop command) at all points where DHCP messages requiring snooping enter the VPLS instance (both from the DHCP server and from the subscribers). Lease state information is extracted from snooped DHCP ACK messages to populate lease state table entries for the SAP.

The optional number-of-entries parameter defines the number lease state table entries allowed.

If number-of-entries is omitted, only a single entry is allowed. Once the maximum number of entries has been reached, subsequent lease state entries are not allowed and subsequent DHCP ACK messages are discarded.

The retained lease state information representing dynamic hosts may be used to:

The no form of the command reverts to the default.

This command enables DHCP Option 82 (Relay Agent Information Option) parameters processing and enters the context for configuring Option 82 sub-options.

The no form of this command reverts to the default.

This command configures the Relay Agent Information Option (Option 82) processing.

The no form of this command reverts to the default.

When enabled, the router sends an ASCII-encoded tuple in the circuit-id sub-option of the DHCP packet. This ASCII-tuple consists of the access-node-identifier, service-id, and SAP-ID, separated by “|”.

In order to send a tuple in the circuit ID, the action replace command must be configured in the same context.

If disabled, the circuit-id sub-option of the DHCP packet will be left empty.

The no form of this command reverts to the default.

This command specifies what information goes into the remote-id sub-option in the DHCP relay packet.

If disabled, the remote-id sub-option of the DHCP packet will be left empty.

The no form of this command reverts to the default.

This command enables the Nokia vendor-specific sub-option of the DHCP relay packet.

The no form of the command reverts to the default.

This command enables the sending of the MAC address in the Nokia vendor-specific sub-option of the DHCP relay packet.

The no form of the command disables the sending of the MAC address in the Nokia vendor-specific sub-option of the DHCP relay packet.

This command sends the pool name in the Nokia vendor specific sub-option of the DHCP relay packet.

The no form of the command reverts to the default.