{"id":852,"date":"2021-08-20T03:07:57","date_gmt":"2021-08-20T03:07:57","guid":{"rendered":"http:\/\/feralpacket.org\/?p=852"},"modified":"2021-08-20T03:07:57","modified_gmt":"2021-08-20T03:07:57","slug":"static-routing-notes","status":"publish","type":"post","link":"https:\/\/feralpacket.org\/?p=852","title":{"rendered":"Static Routing Notes"},"content":{"rendered":"

Static Routing<\/span><\/p>\n

ip route <destination> <direction><\/span><\/p>\n

 – destination<\/p>\n

     -> network<\/p>\n

     -> subnet mask<\/p>\n

 – direction<\/p>\n

     -> exit interface<\/p>\n

     -> next-hop IP<\/p>\n

     -> or both<\/p>\n

Serial interface<\/p>\n

 – Using next-hop IP or interface has no difference<\/p>\n

 – Since there is only one other IP on the serial link<\/p>\n

Multipoint interface<\/p>\n

 – Using interface or next-hop IP address has a big difference<\/p>\n

     -> An ARP request has to be sent<\/p>\n

 – Exit interface<\/p>\n

     -> If a packet arrives at R1 with a destination IP of 50.0.0.1<\/p>\n

     -> Router will do a routing lookup;  since the next-hop IP address is missing, an ARP request is sent for 50.0.0.1<\/p>\n

<\/p>\n

     -> The receiving router (R2) will reply with it’s own MAC address on that segment if proxy-arp is enabled<\/p>\n

          -> A new ARP entry is created for each IP packet sent to R2<\/p>\n

          -> There could be hundreds of ARP entries<\/p>\n

     -> Eventually, the sending router will have a huge ARP table with all IPs  in the 50.0.0.0 network mapped to the MAC address of R2<\/p>\n

     -> Proxy-arp is enabled on routers by default<\/p>\n

 – Next-hop IP address<\/p>\n

     -> Whenever a packet is received for 50.0.0.0, an ARP request will be sent for the next-hop IP address<\/p>\n

 – Next-hop IP address and exit interface<\/p>\n

     -> Whenever a packet is received for 50.0.0.0, an ARP request will be sent for the next-hop IP address<\/p>\n

     -> Scenario based<\/p>\n

          -> Commonly used with BGP<\/p>\n

          -> To prevent routing packets through another service provider<\/p>\n

     -> If both an exit interface and next-hop IP address is used, the network is considered reachable if the exit interface is up<\/p>\n

          -> An ARP request will be sent for the next-hop IP address<\/p>\n

Floating Static Routes<\/span><\/p>\n

ip route 50.0.0.0 255.0.0.0 12.0.0.2<\/span><\/p>\n

ip route 50.0.0.0 255.0.0.0 12.0.0.3 50<\/span><\/p>\n

     -> 50 is the administrative distance<\/p>\n

     -> First route is installed into the routing table<\/p>\n

 – Default administrative distance for static routes is 1<\/p>\n

Recursive Static Route<\/span><\/p>\n

 – When the next-hop is not directly connected<\/p>\n

ip route 50.0.0.0 255.0.0.0 20.0.0.2<\/span><\/p>\n

ip route 20.0.0.0 255.0.0.0 12.0.0.2<\/span><\/p>\n

ip route 20.0.0.0 255.0.0.0 21.0.0.2<\/span><\/p>\n

<\/p>\n

 – Used with BGP loopback to loopback peer netghborship<\/p>\n

 – Will do a recursive lookup for each packet<\/p>\n

     -> Unless CEF is being used<\/p>\n

     -> Cases packets to the load-balanced across the serial links<\/p>\n

Unequal cost load-balancing<\/span><\/p>\n

 – EIGRP<\/p>\n

 – BGP<\/p>\n

<\/p>\n

ip route 20.0.0.0 255.0.0.0 12.0.0.2<\/span><\/p>\n

ip route 30.0.0.0 255.0.0.0 12.0.0.2<\/span><\/p>\n

ip route 40.0.0.0 255.0.0.0 21.0.0.2<\/span><\/p>\n

ip route 50.0.0.0 255.0.0.0 20.0.0.2<\/span><\/p>\n

ip route 50.0.0.0 255.0.0.0 30.0.0.2<\/span><\/p>\n

ip route 50.0.0.0 255.0.0.0 40.0.0.2<\/span><\/p>\n

 – Two packets will be sent to 12.0.0.2 for each packet sent to 21.0.0.2<\/p>\n

 – Recursive lookup is used when CEF is not used<\/p>\n","protected":false},"excerpt":{"rendered":"

Static Routing<\/p>\n","protected":false},"author":1,"featured_media":849,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[31],"class_list":["post-852","post","type-post","status-publish","format-standard","hentry","category-ccie","tag-published"],"_links":{"self":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/852","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=852"}],"version-history":[{"count":1,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/852\/revisions"}],"predecessor-version":[{"id":967,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/852\/revisions\/967"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/media\/849"}],"wp:attachment":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=852"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=852"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=852"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}