Licensing Requirements and Limitations for MPLS LDP
Involved Network Elements
Other network elements are not required.
License Requirements
MPLS is a basic feature of a switch and is not under license control.
Version Requirements
Product Model |
Minimum Version Required |
|---|---|
CE6850-48S6Q-HI |
V100R005C00 |
CE6850-48T6Q-HI/CE6850U-HI/CE6851HI |
V100R005C10 |
CE6855HI |
V200R001C00 |
CE6856HI |
V200R002C50 |
CE6857EI |
V200R005C10 |
CE6860EI |
V200R002C50 |
CE6865EI |
V200R005C00 |
CE6870-24S6CQ-EI/CE6870-48S6CQ-EI |
V200R001C00 |
CE6870-48T6CQ-EI |
V200R002C50 |
CE6875-48S4CQ-EI |
V200R003C00 |
CE7850EI |
V100R003C10 |
CE7855EI |
V200R001C00 |
CE8850-32CQ-EI |
V200R002C50 |
CE8850-64CQ-EI |
V200R005C00 |
CE8860EI |
V100R006C00 |
CE8861E |
V200R005C10 |
CE8868EI |
V200R005C10 |
Feature Limitations
When configuring MPLS LDP on the switch, pay attention to the following points:
- CE switches cannot function as PE devices on an MPLS network.
- RIP-1 cannot run on the MPLS network.
- LDP cannot be restarted during LDP GR.
- For CE7850EI, CE6851HI, CE6850U-HI and CE6850HI series switches:
When used as a transit node, the device cannot load balance the MPLS packets using ECMP.
In V100R005C00 and earlier versions, the device cannot serve as the penultimate hop in PHP scenarios. In V100R005C10 and later versions, if the device serves as the penultimate hop in PHP scenarios and the number of LSPs for which PHP is to be performed is larger than the number of ACLs, you are advised to disable null label distribution on the egress PE device.
- In MPLS PHP scenarios, MPLS QoS on the penultimate hop device becomes invalid:
- When the penultimate hop device receives packets with multiple labels, the EXP priority of outgoing packets remains unchanged.
- When the penultimate hop device receives packets with a single label and the mapping between PHBs and DSCP priorities is enabled on the outbound interface, the DSCP priority of outgoing packets is mapped based on the configured QoS profile. If the mapping between PHBs and DSCP priorities is not enabled on the outbound interface, the DSCP priority of outgoing packets remains unchanged.
- For the CE6870EI/CE6875EI functioning as the penultimate hop device:
If the next hop is an LSP with implicit null label 3 and an LSP with a non-3 label and the LSPs form an ECMP, only one LSP is selected to forward traffic, the ECMP load balancing function becomes invalid, and packets are lost during a link switchover.
If the next hop is an LSP with implicit null label 3 and an LSP with a non-3 label and the LSPs form an FRR, only the primary LSP is selected to forward traffic and the LDP FRR function becomes invalid in versions earlier than V200R019C00. In V200R019C00 and later versions, packets are discarded during an LDP FRR switchover and the switchover has the following impacts:
When the primary LSP uses label 3 and traffic is forwarded through the backup LSP, the traffic is forwarded using the inner label after the outer label is popped out. In this case, the TTL of the inner label in the packet sent by the device is decreased by 1. As a result, the tracert path is incomplete.
- When the primary LSP uses a non-3 label and traffic is forwarded through the backup LSP, label 0 is added to the packets before they are forwarded.
If received MPLS packets contain four or more layers of labels, the CE6870EI and CE6875EI does not load balance the packets based on the IP header using Eth-Trunk or ECMP after popping out the outermost label.
- For CE6870EI and CE6875EIseries switches, if MPLS packets with four or more labels are received, Eth-Trunk or ECMP load balancing cannot be implemented based on the inner IP header.
After removing MPLS labels, switches except CE6870EI and CE6875EI do not load balance MPLS packets through an Eth-Trunk based on the IP header by default. In the PHP scenario, you can configure the mpls top-label src-ip dst-ip 2nd-label command on the penultimate hop to load balance traffic to an Eth-Trunk. You can modify the load balancing profile based on the traffic characteristics to optimize the load balancing effect.
- Layer 3 sub-interfaces on the CE6865EI, CE6857EI, CE8861EI, and CE8868EI do not support MPLS.
- The following operations lead to deletion or re-creation of LDP sessions, causing MPLS service interruption. Exercise caution when performing these operations:
- Change or delete the remote peer IP address or use the IP address as the IP address of a local interface.
- Change the LDP transport address.
- Modify the timeout interval of the Keepalive hold timer.
- Configure LDP MD5 or LDP Keychain authentication.
- Enable or disable LDP GR or modify the timeout interval of LDP GR-related timers.
- When the CE6870EI or CE6875EI is not configured with the MPLS PHP function and uses the inner label to forward packets after the outer label pops up (for example, the switch serves as an ASBR in the inter-AS VPN Option B or inter-AS VPN Option C scenario), the TTL value in the inner label minus 1 is set as the TTL value in the label of packets forwarded by the switch. As a result, an incomplete tracert path is displayed.
- On an MPLS network where packets contain multiple labels, the tracert function may fail to work properly.
- For CE6870EI and CE6875EI series switches, if MPLS functions have been configured on the device, interfaces on the MPLS forwarding path cannot have TRILL functions enabled. Otherwise, MPLS functions do not take effect.
When the system resource mode is set to large-arp or UFT hybrid mode where ARP entries are specified, the device does not support the MPLS function. After the MPLS function is configured, you cannot change the system resource mode to large-arp or specify ARP entries to UFT hybrid mode.
- In an SVF system, if the parent switch supports MPLS LDP, the SVF system supports MPLS LDP in centralized or hybrid mode. If the parent switch and all leaf switches support MPLS LDP, the SVF system supports MPLS LDP in centralized, hybrid or distributed mode.
- MPLS cannot be used together with MUX VLAN.
In V200R003C00 and later versions, the CE6875EI functions as a PE node in an IPv6 VXLAN network. When the CE6875EI also functions as a transit or an egress node in an MPLS network, traffic cannot be load balanced based on the inner IP header.
- When a CE6865EI running V200R005C00, CE6870EI, or CE6875EI functions as a PE node on a VPLS network and the MPLS TTL processing mode is set to uniform, the TTL field of the MPLS label has a fixed value of 255.
- In V200R005C10 and later versions, stacked switches do not support MPLS.
- In the PHP scenarios where non-CE6870EI or non-CE6875EI switches are deployed, you are not advised to configure BFD on the penultimate hop device. Otherwise, extra local BFD session resources are occupied. In addition, when the discriminator of the local BFD session is the same as that of the BFD session established between PEs, the local BFD session cannot go Up.
- When the CE6855HI, CE6856HI, CE6857EI, CE6860EI, CE6865EI, CE7855EI, CE8850EI, CE8860EI, CE8861EI, or CE8868EI switch functions as a penultimate hop device, the implicit null label is enabled, and LSPs whose next hop is label 3 or non-label 3 form multiple paths:
- The switch prefers the LSP with the smallest next-hop IP address among all outbound interfaces as the forwarding path and does not support ECMP fast update.
- In the FRR scenario, only the primary path is selected, and FRR is not supported.
- When LDP load balancing and FRR are used together, OSPF is not supported.
