Overview
This section provides a list of limitations and restrictions for ERSPAN, such as unsupported traffic accounting and specific interface requirements for GRE next hops. Review these constraints to ensure your network configuration supports successful traffic mirroring.
These restrictions apply for ERSPAN
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GRE tunnels are exclusively dedicated to ERSPAN mirrored packets. Do not configure any IPv4 and IPv6 addresses under the GRE tunnel.
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Traffic accounting of the ERSPAN mirrored packets is not supported.
You can view the SPAN packet count per session, using the show monitor-session status internal command.
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ERSPAN decapsulation is not supported.
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ERSPAN does not work if the GRE next hop is reachable over subinterface. For ERSPAN to work, the next hop must be reachable over the main interface. From Cisco IOS XR Software Release 7.5.3 onwards, GRE next hop can be resolved over subinterface or the main interface.
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ERSPAN will be functional regardless of any configuration related to MPLS or LDP present on the router.
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MPLS packet mirroring is supported only from Cisco IOS XR Software Release 7.5.3 onwards.
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On Cisco Silicon One Q100 ASIC-based systems, only the upper 64-bits of the source IPv6 address in the outer IPv6 header of an ERSPAN packet are valid because of data path limitations; the lower 64-bits are set to zero. The destination GREv6 IPv6 address must use the full 128-bit value.
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If you have upgraded the router from Cisco IOS XR Release 24.3.2 to later releases, one of the four user-configured sessions (created in Cisco IOS XR Release 24.3.x) will be lost, as the router allows only a maximum of three user-configured sessions.