Licensing Requirements and Limitations for MPLS LDP
Involved Network Elements
Other network elements are not required.
License Requirements
The MPLS function is controlled by a license. By default, this function is disabled on a newly purchased switch. To use the MPLS function, apply for and purchase the license from the equipment supplier.
Version Requirements
Product Model |
Minimum Version Required |
|---|---|
CE12804/CE12808/CE12812 |
V100R001C00 |
CE12816 |
V100R003C00 |
CE12804S/CE12808S |
V100R005C00 |
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 the switch 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 switch does not load balance the packets based on the IP header using Eth-Trunk or ECMP after popping out the outermost label.
- For CE12800 series 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. In V200R019C00 and later versions, after the assign forward segment-routing hash enhanced command is run, Eth-Trunk or ECMP load balancing can be implemented on MPLS packets with up to five labels.
- 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.
- In V200R002C50, LDP over RSVP TE scenarios do not support MPLS ping and MPLS tracert.
- When the switch 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.
- Among all VSs in port mode, MPLS function can only be configured in the admin-VS.
MPLS function can be configured in any VS in group mode.
- 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.
- MPLS cannot be used together with MUX VLAN.
In V200R003C00 and later versions, the device functions as a PE node in an IPv6 VXLAN network. When the device 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 MPLS packets carry four or more layers of labels (for example, in an IP over segment routing scenario), MPLS packets can be load balanced based on only the three outermost labels using ECMP and Eth-Trunk. In V200R019C00 and later versions, after the assign forward segment-routing hash enhanced command is run, Eth-Trunk or ECMP load balancing can be performed for packets with a maximum of five label stack layers.
- When a switch functions as a PE node on an L2VPN 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.
- When LDP load balancing and FRR are used together, OSPF is not supported.