Consider the following network setup.
A----B----C----D
| |
E----F
The user first configures the option to disable the dynamic bypass tunnels on node B if required. The CLI for this configuration is:
config>router>mpls>dynamic-bypass [disable | enable]
By default, dynamic bypass tunnels are enabled.
Next, the user configures an LSP on node B, such as B-E-F-C to be used only as bypass. The user specifies each hop in the path, for example, the bypass LSP has a strict path.
Note that including the bypass-only keyword disables the following options under the LSP configuration:
bandwidth
fast-reroute
secondary
The following LSP configuration options are allowed:
adaptive
adspec
exclude
hop-limit
include
metric-type
path-computation-method local-cspf
The following example displays a bypass tunnel configuration:
A:ALA-48>config>router>mpls>path# info
-------------------------------------------
...
path "BEFC"
hop 10 10.10.10.11 strict
hop 20 10.10.10.12 strict
hop 30 10.10.10.13 strict
no shutdown
exit
lsp "bypass-BC"
to 10.10.10.15
primary "BEFC"
exit
no shutdown
...
-------------------------------------------
A:ALA-48>config>router>mpls>path#
Next, the user configures an LSP from A to D and indicates fast-reroute bypass protection by selecting facility as the FRR method (config>router>mpls>lsp>fast-reroute facility). If the LSP goes through B, and bypass is requested, and the next hop is C, and there is a manually configured bypass-only tunnel from B to C, excluding link BC, then node B uses that.