{"id":562,"date":"2013-02-12T13:04:24","date_gmt":"2013-02-12T12:04:24","guid":{"rendered":""},"modified":"2018-11-01T00:42:50","modified_gmt":"2018-10-31T23:42:50","slug":"stp-loop-itself-bpdufilter","status":"publish","type":"post","link":"https:\/\/nil.uniza.sk\/en\/stp-loop-itself-bpdufilter\/","title":{"rendered":"STP &#8211; Loop itself with BPDUfilter"},"content":{"rendered":"<p>\n\tWe investigate a special topology condition, where a switch is connected itself on ports Faa0\/1 and Fa0\/2, and one of the port has BPDUFilter feature applied (i.e. simulating STP is switched off). Both ports are in the same vlan (vlan 1 here). The question is:<strong><span style=\"background-color:#ffff00;\"> Is there a topology loop?<\/span><\/strong><\/p>\n<p>\n\t<strong>Initial state<\/strong><\/p>\n<p>\n\tWe check first interfaces status, where we should see that both ports are connected and operational<\/p>\n<pre>\r\nSwitch#sh int status\r\n\r\nPort      Name               Status       Vlan       Duplex  Speed Type\r\nFa0\/1                        connected    1          a-full  a-100 10\/100BaseTX\r\nFa0\/2                        connected    1          a-full  a-100 10\/100BaseTX\r\n<\/pre>\n<p>\n\tsimilarly for observing the spanning tree state of VLAN1:<\/p>\n<pre>\r\nSwitch#sh span vlan 1\r\n\r\nVLAN0001\r\n  Spanning tree enabled protocol ieee\r\n  Root ID    Priority    32769\r\n             Address     001d.e5bc.0580\r\n             This bridge is the root\r\n             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec\r\n\r\n  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)\r\n             Address     001d.e5bc.0580\r\n             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec\r\n             Aging Time  15  sec\r\n\r\nInterface           Role Sts Cost      Prio.Nbr Type\r\n------------------- ---- --- --------- -------- --------------------------------\r\nFa0\/1               Desg FWD 19        128.1    P2p\r\nFa0\/2               Back BLK 19        128.2    P2p\r\n<\/pre>\n<p>\n\tWhere we may see, that in usual condition STP has blocked the Fa0\/2 port. The decision is based on worse BPDU, which is send out of the Fa 0\/2 port (sender PID is the key).<\/p>\n<p>\n\tNow we will apply BPDUFilter on fa 0\/2<\/p>\n<pre>\r\nSwitch(config-if)#span bpdufilter enable<\/pre>\n<p>\n\tand reset the port (apply shutdown and no shutdown because port remains on previous STP state). After that we may observe, that the<\/p>\n<p>\n\tport Fa0\/2 moves through STP states to the <strong>forwarding <\/strong>state<\/p>\n<pre>\r\nSwitch(config-if)#do sh span\r\n\r\nVLAN0001\r\n  Spanning tree enabled protocol ieee\r\n  Root ID    Priority    32769\r\n             Address     001d.e5bc.0580\r\n             This bridge is the root\r\n             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec\r\n\r\n  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)\r\n             Address     001d.e5bc.0580\r\n             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec\r\n             Aging Time  15  sec\r\n\r\nInterface           Role Sts Cost      Prio.Nbr Type\r\n------------------- ---- --- --------- -------- --------------------------------\r\nFa0\/1               Desg FWD 19        128.1    P2p\r\nFa0\/2               Desg <span>FWD <\/span>19        128.2    P2p<\/pre>\n<p>\n\tSo the result is that the bridged <strong>loop has arised<\/strong> and has influence on a switch and network performance.<\/p>\n<p>\n\tNote: the situation is the same if we apply BPDUfilter on the fa0\/1 port.<\/p>\n<p>\n\t&nbsp;<\/p>","protected":false},"excerpt":{"rendered":"<p>\n\tWe investigate a special topology condition, where a switch is connected itself on ports Faa0\/1 and Fa0\/2, and one of the port has BPDUFilter feature applied (i.e. simulating STP is switched off). Both ports are in the same vlan (vlan 1 here). The question is:<strong><span style=\"background-color:#ffff00;\"> Is there a topology loop?<\/span><\/strong><\/p>\n<p>\n\t<strong>Initial state<\/strong><\/p>\n<p>\n\tWe check first interfaces status, where we should see that both ports are connected and operational<\/p>","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"footnotes":""},"categories":[697,701,703],"tags":[],"class_list":["post-562","post","type-post","status-publish","format-standard","hentry","category-ccna-en","category-ccnp-en","category-exercises-en"],"taxonomy_info":{"category":[{"value":697,"label":"CCNA"},{"value":701,"label":"CCNP"},{"value":703,"label":"Exercises"}]},"featured_image_src_large":false,"author_info":{"display_name":"admin","author_link":"https:\/\/nil.uniza.sk\/en\/author\/admin\/"},"comment_info":2,"category_info":[{"term_id":697,"name":"CCNA","slug":"ccna-en","term_group":0,"term_taxonomy_id":695,"taxonomy":"category","description":"","parent":695,"count":12,"filter":"raw","cat_ID":697,"category_count":12,"category_description":"","cat_name":"CCNA","category_nicename":"ccna-en","category_parent":695},{"term_id":701,"name":"CCNP","slug":"ccnp-en","term_group":0,"term_taxonomy_id":699,"taxonomy":"category","description":"","parent":695,"count":8,"filter":"raw","cat_ID":701,"category_count":8,"category_description":"","cat_name":"CCNP","category_nicename":"ccnp-en","category_parent":695},{"term_id":703,"name":"Exercises","slug":"exercises-en","term_group":0,"term_taxonomy_id":701,"taxonomy":"category","description":"","parent":695,"count":1,"filter":"raw","cat_ID":703,"category_count":1,"category_description":"","cat_name":"Exercises","category_nicename":"exercises-en","category_parent":695}],"tag_info":false,"_links":{"self":[{"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/posts\/562","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/comments?post=562"}],"version-history":[{"count":0,"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/posts\/562\/revisions"}],"wp:attachment":[{"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/media?parent=562"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/categories?post=562"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nil.uniza.sk\/en\/wp-json\/wp\/v2\/tags?post=562"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}