{"id":2101,"date":"2011-05-07T21:51:36","date_gmt":"2011-05-07T21:51:36","guid":{"rendered":"http:\/\/wiki.freeiz.com\/?p=2101"},"modified":"2016-08-09T12:08:27","modified_gmt":"2016-08-09T12:08:27","slug":"cisco-storm-control","status":"publish","type":"post","link":"https:\/\/wiki-see.info\/wp\/2011\/05\/07\/cisco-storm-control\/","title":{"rendered":"Cisco Storm Control"},"content":{"rendered":"

I remember when I first saw Storm Control<\/span> in a config and thought \u201cwoah<\/span>, whats that looks
\nreally confusing\u201d, but really its pretty simple stuff<\/span>.<\/span><\/p>\n

We use storm control<\/span> to rate limit layer 2 traffic, this helps us prevent a subnet from being
\nflooded<\/span> with broadcasts<\/span>, multicasts <\/span>which would adversely affect the performance of the entire subnet.<\/span><\/p>\n

Storm Control <\/span>can only be configured on<\/span> physical interfaces<\/span> and will not work on<\/span> subinterfaces<\/span>,
\n or an LACP\/PAGP interface<\/span>.<\/p>\n

Configuration<\/span><\/strong><\/p>\n

The first command<\/span> shown limits the broadcast<\/span> to 200pps, and if this limit is reached will not forward
\nany more broadcasts until this is reduced to 150pps.<\/span><\/p>\n

(config-if)#storm-control broadcast level pps 200 150<\/strong><\/span><\/p>\n

Multicast<\/span> and unicast<\/span> traffic can also be limited, the maximum level can also be entered as a percentage<\/span>
\ninstead of pps<\/span>, in the example below multicasts can use up to 5%<\/span> of the interface bandwidth<\/span>,
\nand once that\u00a0limit is reach no more multicasts<\/span> will be forwarded until it drops to 4.5%<\/span> of the total
\ninterface bandwidth<\/span><\/p>\n

(config-if)#storm-control multicast level 5 4.5<\/strong><\/span><\/p>\n

In the final example<\/span> unicast<\/span> is limited to 80%<\/span> of the interface bandwidth but a second value is not
\nspecified, this causes all unicast to be forwarded up to 80% of the bandwidth and it does not force the
\ntraffic to wait until it drops below a second level.<\/span><\/p>\n

(config-if)#storm-control unicast level 80<\/strong><\/span><\/p>\n

The default response for storm control<\/span> is the drop packets which are over the rate limit, and create a
\n syslog message<\/span>, we can also generate a SNMP trap<\/span> with the command<\/span><\/p>\n

(config-if)#storm-control action trap<\/strong><\/span><\/p>\n

The show commands for this are also really easy<\/span> :
\n (config-if)#show storm-control<\/strong> port <\/em>[unicast<\/strong>|broadcast<\/strong>|multicast<\/strong>]<\/span><\/span><\/p>\n

Configuration Sample<\/span> :<\/p>\n

Understanding Storm Control<\/span><\/h3>\n
<\/pre>\n
Storm control prevents traffic on a LAN from being disrupted by a broadcast<\/span>, <\/span>
\nmulticast<\/span>, or unicast<\/span> storm on one of the physical interfaces<\/span>.<\/p>\n
A value of 0.0 means that all broadcast<\/span>, multicast<\/span>, or unicast<\/span> traffic on that <\/span>
\nport is blocked.<\/span><\/p>\n
config t <\/span>
\nint fa0\/1 <\/span>
\nstorm-control broadcast level 80.00 50.00 <\/span>
\n storm-control multicast level 80.00 50.00 <\/span>
\n storm-control unicast level 80.00 50.00 <\/span>
\n storm-control action shutdown <\/span>
\n storm-control action trap<\/span><\/p>\n
Switch(config-if)# storm-control broadcast level 0 <\/span><\/span>
\nSwitch(config-if)# storm-control unicast level 0 <\/span><\/span>
\nSwitch(config-if)# storm-control multicast level 0<\/span><\/span><\/p>\n
My understanding of “switchport block multicast<\/span>” is that it blocks flooding of multicast<\/span> traffic to ports
\nthat are unknown or unjoined for a particular multicast group. <\/span><\/span><\/p>\n
This seems to be a <\/span>layer 2 multicast control<\/span>?
\n“Note <\/strong>Only pure Layer 2 multicast traffic is blocked. Multicast packets that contain IPv4 or IPv6
\ninformation in the header are not blocked<\/span>.”<\/p>\n
 So same concept, but different layers!\u00a0 The “switchport block” whether unicast or multicast is designed
\nto affect the Layer2 flooding concepts for unknown unicasts or multicast frames.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"
I remember when I first saw Storm Control in a config and thought \u201cwoah, whats that looks really confusing\u201d, but really its pretty simple stuff. We use storm control to rate limit layer 2 traffic, this helps us prevent a subnet from being flooded with broadcasts, multicasts which would adversely affect the performance of the […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[654],"class_list":["post-2101","post","type-post","status-publish","format-standard","hentry","category-cisco-routers","tag-storm-control"],"_links":{"self":[{"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/posts\/2101","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/comments?post=2101"}],"version-history":[{"count":1,"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/posts\/2101\/revisions"}],"predecessor-version":[{"id":5080,"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/posts\/2101\/revisions\/5080"}],"wp:attachment":[{"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/media?parent=2101"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/categories?post=2101"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wiki-see.info\/wp\/wp-json\/wp\/v2\/tags?post=2101"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}