SNMP Support
************

SNMP (Simple Network Managing Protocol) is a widely implemented
feature for collecting network information from router and/or host.
FRR itself does not support SNMP agent (server daemon) functionality
but is able to connect to a SNMP agent using the the AgentX protocol
(**RFC 2741**) and make the routing protocol MIBs available through
it.

Note that SNMP Support needs to be enabled at compile-time and loaded
as module on daemon startup. Refer to Loadable Module Support on the
latter.


Getting and installing an SNMP agent
====================================

The supported SNMP agent is AgentX. We recommend to use the latest
version of *net-snmp* which was formerly known as *ucd-snmp*. It is
free and open software and available at http://www.net-snmp.org/ and
as binary package for most Linux distributions.


AgentX configuration
====================

To enable AgentX protocol support, FRR must have been build with the "
--enable-snmp" or *--enable-snmp=agentx* option. Both the master SNMP
agent (snmpd) and each of the FRR daemons must be configured. In
"/etc/snmp/snmpd.conf", the "master agentx" directive should be added.
In each of the FRR daemons, "agentx" command will enable AgentX
support.

"/etc/snmp/zebra.conf":

   #
   # example access restrictions setup
   #
   com2sec readonly default public
   group MyROGroup v1 readonly
   view all included .1 80
   access MyROGroup "" any noauth exact all none none
   #
   # enable master agent for AgentX subagents
   #
   master agentx

"/etc/frr/ospfd.conf:"

      ! ... the rest of ospfd.conf has been omitted for clarity ...
      !
      agentx
      !

Upon successful connection, you should get something like this in the
log of each FRR daemons:

   2012/05/25 11:39:08 ZEBRA: snmp[info]: NET-SNMP version 5.4.3 AgentX subagent connected

Then, you can use the following command to check everything works as
expected:

   # snmpwalk -c public -v1 localhost .1.3.6.1.2.1.14.1.1
   OSPF-MIB::ospfRouterId.0 = IpAddress: 192.168.42.109
   [...]

The AgentX protocol can be transported over a Unix socket or using TCP
or UDP. It usually defaults to a Unix socket and depends on how
NetSNMP was built. If need to configure FRR to use another transport,
you can configure it through "/etc/snmp/frr.conf":

   [snmpd]
   # Use a remote master agent
   agentXSocket tcp:192.168.15.12:705

Here is the syntax for using AgentX:

agentx

no agentx


Handling SNMP Traps
===================

To handle snmp traps make sure your snmp setup of frr works correctly
as described in the frr documentation in SNMP Support.

The BGP4 mib will send traps on peer up/down events. These should be
visible in your snmp logs with a message similar to:

   snmpd[13733]: Got trap from peer on fd 14

To react on these traps they should be handled by a trapsink.
Configure your trapsink by adding the following lines to
"/etc/snmpd/snmpd.conf":

   # send traps to the snmptrapd on localhost
   trapsink localhost

This will send all traps to an snmptrapd running on localhost. You can
of course also use a dedicated management station to catch traps.
Configure the snmptrapd daemon by adding the following line to
"/etc/snmpd/snmptrapd.conf":

   traphandle .1.3.6.1.4.1.3317.1.2.2 /etc/snmp/snmptrap_handle.sh

This will use the bash script "/etc/snmp/snmptrap_handle.sh" to handle
the BGP4 traps. To add traps for other protocol daemons, lookup their
appropriate OID from their mib. (For additional information about
which traps are supported by your mib, lookup the mib on
http://www.oidview.com/mibs/detail.html).

Make sure *snmptrapd* is started.

The snmptrap_handle.sh script I personally use for handling BGP4 traps
is below. You can of course do all sorts of things when handling
traps, like sound a siren, have your display flash, etc., be creative
;).

   #!/bin/bash

   # routers name
   ROUTER=`hostname -s`

   #email address use to sent out notification
   EMAILADDR="john@doe.com"
   #email address used (allongside above) where warnings should be sent
   EMAILADDR_WARN="sms-john@doe.com"

   # type of notification
   TYPE="Notice"

   # local snmp community for getting AS belonging to peer
   COMMUNITY="<community>"

   # if a peer address is in $WARN_PEERS a warning should be sent
   WARN_PEERS="192.0.2.1"

   # get stdin
   INPUT=`cat -`

   # get some vars from stdin
   uptime=`echo $INPUT | cut -d' ' -f5`
   peer=`echo $INPUT | cut -d' ' -f8 | sed -e 's/SNMPv2-SMI::mib-2.15.3.1.14.//g'`
   peerstate=`echo $INPUT | cut -d' ' -f13`
   errorcode=`echo $INPUT | cut -d' ' -f9 | sed -e 's/\\"//g'`
   suberrorcode=`echo $INPUT | cut -d' ' -f10 | sed -e 's/\\"//g'`
   remoteas=`snmpget -v2c -c $COMMUNITY localhost SNMPv2-SMI::mib-2.15.3.1.9.$peer | cut -d' ' -f4`

   WHOISINFO=`whois -h whois.ripe.net " -r AS$remoteas" | egrep '(as-name|descr)'`
   asname=`echo "$WHOISINFO" | grep "^as-name:" | sed -e 's/^as-name://g' -e 's/  //g' -e 's/^ //g' | uniq`
   asdescr=`echo "$WHOISINFO" | grep "^descr:" | sed -e 's/^descr://g' -e 's/  //g' -e 's/^ //g' | uniq`

   # if peer address is in $WARN_PEER, the email should also
   # be sent to $EMAILADDR_WARN
   for ip in $WARN_PEERS; do
   if [ "x$ip" == "x$peer" ]; then
   EMAILADDR="$EMAILADDR,$EMAILADDR_WARN"
   TYPE="WARNING"
   break
   fi
   done

   # convert peer state
   case "$peerstate" in
   1) peerstate="Idle" ;;
   2) peerstate="Connect" ;;
   3) peerstate="Active" ;;
   4) peerstate="Opensent" ;;
   5) peerstate="Openconfirm" ;;
   6) peerstate="Established" ;;
   *) peerstate="Unknown" ;;
   esac

   # get textual messages for errors
   case "$errorcode" in
   00)
   error="No error"
   suberror=""
   ;;
   01)
   error="Message Header Error"
   case "$suberrorcode" in
   01) suberror="Connection Not Synchronized" ;;
   02) suberror="Bad Message Length" ;;
   03) suberror="Bad Message Type" ;;
   *) suberror="Unknown" ;;
   esac
   ;;
   02)
   error="OPEN Message Error"
   case "$suberrorcode" in
   01) suberror="Unsupported Version Number" ;;
   02) suberror="Bad Peer AS" ;;
   03) suberror="Bad BGP Identifier" ;;
   04) suberror="Unsupported Optional Parameter" ;;
   05) suberror="Authentication Failure" ;;
   06) suberror="Unacceptable Hold Time" ;;
   *) suberror="Unknown" ;;
   esac
   ;;
   03)
   error="UPDATE Message Error"
   case "$suberrorcode" in
   01) suberror="Malformed Attribute List" ;;
   02) suberror="Unrecognized Well-known Attribute" ;;
   03) suberror="Missing Well-known Attribute" ;;
   04) suberror="Attribute Flags Error" ;;
   05) suberror="Attribute Length Error" ;;
   06) suberror="Invalid ORIGIN Attribute" ;;
   07) suberror="AS Routing Loop" ;;
   08) suberror="Invalid NEXT_HOP Attribute" ;;
   09) suberror="Optional Attribute Error" ;;
   10) suberror="Invalid Network Field" ;;
   11) suberror="Malformed AS_PATH" ;;
   *) suberror="Unknown" ;;
   esac
   ;;
   04)
   error="Hold Timer Expired"
   suberror=""
   ;;
   05)
   error="Finite State Machine Error"
   suberror=""
   ;;
   06)
   error="Cease"
   case "$suberrorcode" in
   01) suberror="Maximum Number of Prefixes Reached" ;;
   02) suberror="Administratively Shutdown" ;;
   03) suberror="Peer Unconfigured" ;;
   04) suberror="Administratively Reset" ;;
   05) suberror="Connection Rejected" ;;
   06) suberror="Other Configuration Change" ;;
   07) suberror="Connection collision resolution" ;;
   08) suberror="Out of Resource" ;;
   09) suberror="MAX" ;;
   *) suberror="Unknown" ;;
   esac
   ;;
   *)
   error="Unknown"
   suberror=""
   ;;
   esac

   # create textual message from errorcodes
   if [ "x$suberror" == "x" ]; then
   NOTIFY="$errorcode ($error)"
   else
   NOTIFY="$errorcode/$suberrorcode ($error/$suberror)"
   fi

   # form a decent subject
   SUBJECT="$TYPE: $ROUTER [bgp] $peer is $peerstate: $NOTIFY"
   # create the email body
   MAIL=`cat << EOF
   BGP notification on router $ROUTER.

   Peer: $peer
   AS: $remoteas
   New state: $peerstate
   Notification: $NOTIFY

   Info:
   $asname
   $asdescr

   Snmpd uptime: $uptime
   EOF`

   # mail the notification
   echo "$MAIL" | mail -s "$SUBJECT" $EMAILADDR