Configuring a GRE Tunnel to Copy ToS Bits to the Outer IP Header
Unlike IP-IP tunnels, GRE tunnels do not copy the ToS
bits to the outer IP header by default. To copy the inner ToS bits
to the outer IP header (which is required for some tunneled routing
protocols) on packets sent by the Routing Engine, include the copy-tos-to-outer-ip-header statement at the logical unit hierarchy
level of a GRE interface. To copy the inner ToS bits to the outer
IP header on packets transiting the device (MX Series routers with
MPCs only), include the copy-tos-to-outer-ip-header-transit statement at the logical unit hierarchy level of a GRE interface.
To copy the inner ToS bits to the outer IP header on a GRE tunnel:
Specify the interface on which to enable the inner IP header’s ToS bits to be copied to the outer IP packet header
[edit] user@host# edit interfaces user@host# set gr-0/0/0 unit 0 copy-tos-to-outer-ip-header user@host# set gr-0/0/0 unit 0 copy-tos-to-outer-ip-header-transit user@host# set gr-0/0/0 unit 0 family inet
You can also copy the inner ToS bits to the outer IP header
on packets transiting the device on a global basis for all GRE interfaces
on MPCs by including the copy-tos-to-outer service-type gre statement at the [edit chassis] hierarchy level. This
statement affects all GRE interfaces on MPCs and takes precedence
over the copy-tos-to-outer-ip-header-transit statement.
Once committed, this configuration statement only affects new gr- interfaces. To affect an existing gr- interface,
you must delete and re-add the interface.
To
verify that this option is enabled at the interface level, use the show interfaces interface-name detail command.