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-rw-r--r--docs/gettingstarted/developers/vlib.md48
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diff --git a/docs/gettingstarted/developers/vlib.md b/docs/gettingstarted/developers/vlib.md
index 13844ab455a..59206e5ed4b 100644
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+++ b/docs/gettingstarted/developers/vlib.md
@@ -540,6 +540,54 @@ certain cli command has the potential to hurt packet processing
performance by running for too long, do the work incrementally in a
process node. The client can wait.
+### Macro expansion
+
+The vpp debug CLI engine includes a recursive macro expander. This
+is quite useful for factoring out address and/or interface name
+specifics:
+
+```
+ define ip1 192.168.1.1/24
+ define ip2 192.168.2.1/24
+ define iface1 GigabitEthernet3/0/0
+ define iface2 loop1
+
+ set int ip address $iface1 $ip1
+ set int ip address $iface2 $(ip2)
+
+ undefine ip1
+ undefine ip2
+ undefine iface1
+ undefine iface2
+```
+
+Each socket (or telnet) debug CLI session has its own macro
+tables. All debug CLI sessions which use CLI_INBAND binary API
+messages share a single table.
+
+The macro expander recognizes circular defintions:
+
+```
+ define foo \$(bar)
+ define bar \$(mumble)
+ define mumble \$(foo)
+```
+
+At 8 levels of recursion, the macro expander throws up its hands and
+replies "CIRCULAR."
+
+### Macro-related debug CLI commands
+
+In addition to the "define" and "undefine" debug CLI commands, use
+"show macro [noevaluate]" to dump the macro table. The "echo" debug
+CLI command will evaluate and print its argument:
+
+```
+ vpp# define foo This\ Is\ Foo
+ vpp# echo $foo
+ This Is Foo
+```
+
Handing off buffers between threads
-----------------------------------