{"id":821,"date":"2021-08-20T03:09:47","date_gmt":"2021-08-20T03:09:47","guid":{"rendered":"http:\/\/feralpacket.org\/?p=821"},"modified":"2021-08-20T03:09:47","modified_gmt":"2021-08-20T03:09:47","slug":"switching-notes","status":"publish","type":"post","link":"https:\/\/feralpacket.org\/?p=821","title":{"rendered":"Switching Notes"},"content":{"rendered":"

Layer 2<\/span> <\/p>\n

<\/p>\n

ACL –> Frame allowed \/ denied<\/p>\n

QoS –> Priority frame marking<\/p>\n

CAM –> next-hop information -> exit interface <\/p>\n

   |<\/p>\n

   |–> All three operations are performed at the same time using dedicated co-processors (ASICs)<\/p>\n

Terney Content Addressable Memory<\/p>\n

 – 3 values (VMR)<\/p>\n

     – Value<\/p>\n

     – Mask<\/p>\n

     – Result<\/p>\n

If destination is starting with 10.x.x.x, then deny<\/p>\n

 – 10.x.x.x               –> Value<\/p>\n

 – 0.255.255.255     –> Mask<\/p>\n

 – Deny                   –> Result<\/p>\n

show mac address-table<\/p>\n

 –> Vlan<\/p>\n

 –> MAC address<\/p>\n

 –> Type (how learned)<\/p>\n

 –> Ports (exit interface)<\/p>\n

Layer 3<\/span><\/p>\n

<\/p>\n

FIB –> Forwarding Information Base<\/p>\n

PR –> Packet Rewrite<\/p>\n

CEF –> Cisco Express Forwarding<\/p>\n

PR<\/p>\n

 – rewrite TTL (IP headers)<\/p>\n

 – MAC source \/ destination<\/p>\n

 – IP checksum<\/p>\n

 – ethernet CRC<\/p>\n

show ip cef<\/span><\/p>\n

 -> Prefix<\/p>\n

 -> Next-hop<\/p>\n

     -> no route<\/p>\n

     -> receive<\/p>\n

     -> drop<\/p>\n

 -> Interface<\/p>\n

Switching is all about interfaces<\/p>\n

Interface Modes<\/p>\n

 -> Access – connected to end devices<\/p>\n

 -> Trunk – connected to other switches<\/p>\n

 -> Tunnel – Q in Q tunnel<\/p>\n

int fa0\/1<\/span><\/p>\n

 switchport mode { access | trunk }<\/span><\/p>\n

Tunnel mode is configured in access mode<\/p>\n

int range fa0\/1 – 5<\/span><\/p>\n

int range fa0\/1, fa0\/5 – 8 , fa0\/15<\/span><\/p>\n

define interface ABC fa0\/1, fa0\/5 – 8<\/span><\/p>\n

int range macro ABC<\/span><\/p>\n

Trunking<\/span><\/p>\n

 -> ISL – Inter-Switch Link<\/p>\n

 -> 802.1Q – IEEE standard<\/p>\n

ISL<\/p>\n

 -> not in the R&S v5 lab<\/p>\n

 -> Cisco proprietary<\/p>\n

 -> 30 bytles additionally added to the frame<\/p>\n

 ——————–<\/p>\n

 | 26 | frame | 4 |<\/p>\n

 ———————<\/p>\n

 -> only 15 bits used to identify the VLAN<\/p>\n

 -> no untagged VLAN<\/p>\n

802.1Q<\/p>\n

 -> 4 bytes added to the frame<\/p>\n

   6      6      4      up to 1500 bytes  4<\/p>\n

————————————————-<\/p>\n

| DA | SA | .1q | type | data………| FCS |<\/p>\n

————————————————-<\/p>\n

                   ^<\/p>\n

 -> 12 bits<\/p>\n

     -> 2^12 VLANs –> 4096<\/p>\n

          0 to 4095<\/p>\n

               -> Vlan 0 (hidden system VLAN)<\/p>\n

               -> Vlan 4095 (hidden system VLAN)<\/p>\n

               -> Vlans 1 – 4094 usable<\/p>\n

Normal frame<\/p>\n

 -> 1518 bytes<\/p>\n

802.1Q frame<\/p>\n

 -> 1522 bytes<\/p>\n

Vlan 1<\/p>\n

 -> Management VLAN<\/p>\n

 -> Default native VLAN<\/p>\n

     -> untagged VLAN<\/p>\n

 -> used for:<\/p>\n

     -> CDP packets<\/p>\n

     -> VTP packets<\/p>\n

     -> STP packets<\/p>\n

 -> Shutting down VLAN 1 only affects data traffic<\/p>\n

 -> All switching protocols use VLAN 1<\/p>\n

VLANs 1002 – 1005<\/p>\n

 -> Tolken Ring VLANs<\/p>\n

ISL<\/p>\n

 -> VLANs 1 – 1001<\/p>\n

Reduced MAC Address feature<\/p>\n

 – One VLAN -> priority number + Base MAC address<\/p>\n

 – Configured with:<\/p>\n

     -> SW1(config)# spanning-tree extended system-id<\/span><\/p>\n

     -> Default configuration<\/p>\n

     -> Required to create more than 1001 VLANs<\/p>\n

SW1<\/p>\n

 – priority number: 32768<\/p>\n

 – Base MAC address:  0001.0002.0003<\/p>\n

 – VLAN 10:  32768.0001.0002.0003<\/p>\n

 – VLAN 11:  32769.0001.0002.0003<\/p>\n

Spanning Tree Protocol (801.2D)<\/p>\n

 -> used to prevent loops while maintaining redundancy<\/p>\n","protected":false},"excerpt":{"rendered":"

Layer 2\u00a0<\/p>\n","protected":false},"author":1,"featured_media":819,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[31,60],"class_list":["post-821","post","type-post","status-publish","format-standard","hentry","category-ccie","tag-published","tag-switching"],"_links":{"self":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/821","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=821"}],"version-history":[{"count":1,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/821\/revisions"}],"predecessor-version":[{"id":976,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/821\/revisions\/976"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/media\/819"}],"wp:attachment":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=821"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=821"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=821"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}