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diff --git a/docs/gettingstarted/developers/fib20/debugging.rst b/docs/gettingstarted/developers/fib20/debugging.rst new file mode 100644 index 00000000000..e0a85fd736e --- /dev/null +++ b/docs/gettingstarted/developers/fib20/debugging.rst @@ -0,0 +1,106 @@ +.. _debugging: + +Debugging +--------- + +the anatomy of a route: + +.. code-block:: console + + BGvpp# sh ip fib 1.1.1.3/32 + ipv4-VRF:0, fib_index:0, flow hash:[src dst sport dport proto ] epoch:0 flags:none locks:[adjacency:1, recursive-resolution:4, default-route:1, ] + 1.1.1.0/24 fib:0 index:9 locks:2 + CLI refs:1 src-flags:added,contributing,active, + path-list:[24] locks:4 flags:shared, uPRF-list:11 len:1 itfs:[1, ] + path:[26] pl-index:24 ip4 weight=1 pref=0 attached-nexthop: oper-flags:resolved, + 10.0.0.1 loop0 + [@0]: arp-ipv4: via 10.0.0.1 loop0 + + forwarding: unicast-ip4-chain + [@0]: dpo-load-balance: [proto:ip4 index:11 buckets:1 uRPF:11 to:[0:0]] + [0] [@3]: arp-ipv4: via 10.0.0.1 loop0 + +let's go line by line. + +.. code-block:: console + + ipv4-VRF:0, fib_index:0, flow hash:[src dst sport dport proto ] epoch:0 flags:none locks:[adjacency:1, recursive-resolution:4, default-route:1, ] + +Each field in turn: + +- ipv4-VRF:0: the name of the table (as given by the user, or + automatically generated by VPP). +- fib-index:0; in the VPP pool of FIB objects, this is index 0 +- flow hash:[src dst sport dport proto ]: When calculating the flow + hash to use for load-balanacing, these are the fields in the packet + that are used. There is an API to change this per-table. +- epoch:0; Used during mark-n-sweep. +- flags:none; use the force, to find the per-table flags. +- locks: per-source reference counting, a table can only be deleted + when all sources no longer reference it. + +next line: + +.. code-block:: console + + 1.1.1.0/24 fib:0 index:9 locks:2 + +this shows the route that matched the show request. note that it is not +an exact match, it's an LPM. The route is in FIB index 0, its index +(in the VPP pool of fib_entry_t objects) is nine and there are two +references to the entry. +You'll get the same output if you type "sh fib entry 9" + +next line: + +.. code-block:: console + + CLI refs:1 src-flags:added,contributing,active, + +the 'CLI' has sourced this route (it was added via CLI). This source +has been added (well duh) it is 'active', meaning it is the best +source, and it is contributing a forwarding object. There are some +scenarios where sources other than the active source contribute, +namely interpose sources. + +next line: + +.. code-block:: console + + path-list:[24] locks:4 flags:shared, uPRF-list:11 len:1 itfs:[1, ] + +This is path-list inex 24 (see "sh fib path-list 24" this will also +show the children), it is 'shared', +meaning that if other prefixes were to use the same set of paths, +then they would also use this path-list object. It has uRPF list 11 of +length 1 containing interface index 1 (which is loop0, see "sh int"). + +next line: + +.. code-block:: console + + path:[26] pl-index:24 ip4 weight=1 pref=0 attached-nexthop: oper-flags:resolved, + 10.0.0.1 loop0 + [@0]: arp-ipv4: via 10.0.0.1 loop0 + +This is path 26 (see "sh fib path 26"). It's a member of +path-list 24. It's ip4 has a weight of 1 and a preference of 0. It's +of type 'attached-nexthop' and currently resolved - woohoo. +It is a path 'via 10.0.0.1 loop0'. It is contributing an incomplete adjacency. + +next line: + +.. code-block:: console + + forwarding: unicast-ip4-chain + [@0]: dpo-load-balance: [proto:ip4 index:11 buckets:1 uRPF:11 to:[0:0]] + [0] [@3]: arp-ipv4: via 10.0.0.1 loop0 + +This section describes how packets of type 'unicast-ip4' will be +forwarded. It is the result of processing the path information from +above. +Here we see load-balance object 11, which has 1 bucket/choice. It is +also linked to uRPF instance 11 (which it got from path-list 24). +In bucket 0 there is the incomplete adjacnecy that was contributed by +path 26. + |