{"id":213,"date":"2015-01-03T09:01:54","date_gmt":"2015-01-03T09:01:54","guid":{"rendered":"http:\/\/feralpacket.org\/?p=213"},"modified":"2015-01-03T11:15:13","modified_gmt":"2015-01-03T11:15:13","slug":"is-is-notes","status":"publish","type":"post","link":"https:\/\/feralpacket.org\/?p=213","title":{"rendered":"IS-IS Notes"},"content":{"rendered":"

<\/p>\n

IS-IS<\/b><\/p>\n

– Link state routing protocol<\/p>\n

-> 0xFEFE<\/p>\n

-> 0x0800<\/p>\n

– Connectionless Network Protocol (CLNP)<\/p>\n

– Like an IP protocol suite in OSI model<\/p>\n

-> Router<\/p>\n

-> Intermediate System (IS)<\/p>\n

-> End host<\/p>\n

-> End System (ES)<\/p>\n

-> OSI protocol<\/p>\n

-> Directly works over layer 2<\/p>\n

-> Integrated IS-IS can have payload of IPv4 or IPv6<\/p>\n

 <\/p>\n

IS-IS uses the following parameters<\/b><\/p>\n

– IS-IS Hello (IIH)<\/p>\n

– Link State Packet (LSP)<\/p>\n

-> Database IS-IS<\/p>\n

– Complete Sequence Number PDU (CSNP)<\/p>\n

-> A list of database entries<\/p>\n

– Partial Sequence Number PDU (PSNP)<\/p>\n

-> A request to send LSPs<\/p>\n

 <\/p>\n

\"20141006_124520-1\"<\/a><\/p>\n

 <\/p>\n

Neighbor Formation<\/b><\/p>\n

– IIH must match the following<\/p>\n

-> Authentication<\/p>\n

-> IS type<\/p>\n

-> MTU<\/p>\n

-> Priority<\/p>\n

-> system-id \/ area-id<\/p>\n

 <\/p>\n

Link can be point-to-point or multi-access<\/b><\/p>\n

– Network types<\/p>\n

-> Point-to-point<\/p>\n

-> Broadcast<\/p>\n

-> DIS is elected (Designated Intermediate System)<\/p>\n

-> Highest priority selected<\/p>\n

-> Highest Subnet Point of Attachment (SNPA)<\/p>\n

-> MAC address (ethernet)<\/p>\n

-> Frame-relay DLCI<\/p>\n

-> Highest system-id<\/p>\n

-> DIS election is pre-emptive<\/p>\n

 <\/p>\n

SNAP Address<\/b><\/p>\n

– Subnetwork Access Point<\/p>\n

– 20 butes represented in HEX<\/p>\n

-> Bytes 1 – 13<\/p>\n

-> area-id<\/p>\n

-> Bytes 14 – 20<\/p>\n

-> Network Selector Field<\/p>\n

-> Always equal to “00”<\/p>\n

A SNAP address with a NSEL part 0 Network Entity Title (NET) address<\/p>\n

-> Must be an even number of bytes<\/p>\n

 <\/p>\n

IS-IS Area and Backbone Network<\/b><\/p>\n

– Level-1<\/p>\n

-> Router configuration mode<\/p>\n

-> Similar to a NSSA<\/p>\n

– Level-2<\/p>\n

-> Interface configuration mode<\/p>\n

-> Similar to Area 0 routers<\/p>\n

– Level-1-2<\/p>\n

– The level decides which updates can be received<\/p>\n

– Two routers can be in different areas and still form neighbors<\/p>\n

-> This means IS-IS areas are per router, as opposed to OSPF which is area per-link<\/p>\n

 <\/p>\n

\"20141006_124553-1\"<\/a><\/p>\n

 <\/p>\n

\"20141006_124559-1\"<\/a><\/p>\n

 <\/p>\n

All routers and links, by default, are Level-1-2<\/p>\n

– Within an area, L-1-2 neighbors can be formed<\/p>\n

– Between areas, only L-2 neighbors can be formed<\/p>\n

– A consecutive set of Level-2 adjacencies is called a backbone, which may include several routers<\/p>\n

-> The Level-2 adjacencies cannot be discontiguous<\/p>\n

– The Level-1-2 router on the edge will send all Level-1 LSP with attached it set towards Level-1 routers<\/p>\n

 <\/p>\n

IS-IS Data Flow Procedures<\/b><\/p>\n

– Receive operation<\/p>\n

-> Updates are received as LSP<\/p>\n

– Update operation<\/p>\n

-> Updates are sent as LSP<\/p>\n

– Decision operation<\/p>\n

-> SPF algorithm finding the best routes<\/p>\n

– Forward operation<\/p>\n

-> Create CEF table entries with the best routes<\/p>\n

 <\/p>\n

IS-IS Metric<\/b><\/p>\n

– Metric is cost<\/p>\n

– Cost is constant 10 everywhere<\/p>\n

-> No calculation<\/p>\n

– By default, “narrow metric” is used<\/p>\n

-> 6 bit<\/p>\n

-> 1 – 63<\/p>\n

– Can be changed to “wide metric”<\/p>\n

-> 2^24<\/p>\n

–\u00a0\u201cWide metric\u201d is needed for MPLS TE<\/p>\n

 <\/p>\n

IS-IS Topology<\/b><\/p>\n

– Single topology<\/p>\n

-> IPv4 and IPv6 address-families share the same path calculation<\/p>\n

-> IPv4 and IPv6 has to be enabled on all interfaces configured for IS-IS<\/p>\n

-> The interfaces doesn\u2019t necessarily need both IPv4 and \/\u00a0or IPv6 addresses configured<\/p>\n

– Multi topology<\/p>\n

-> IPv4 and IPv6 address-families calculate best paths\u00a0independently<\/p>\n

-> IPv4 and IPv6 configuration independent<\/p>\n

-> Interfaces configured for IS-IS can have IPv4 enabled, IPv6 enabled, or both<\/p>\n

– For IOS routers, the default configuration is single topology<\/p>\n

– For XR routers, the default configuration is multi\u00a0topology<\/p>\n

 <\/p>\n

\"20141006_124610-1\"<\/a><\/p>\n

 <\/p>\n

Configuring IS-IS<\/b><\/p>\n

IOS Router<\/p>\n

(config)# router isis [<name>}<\/span><\/p>\n

-> default name is NULL<\/p>\n

\u00a0net 49.001.0000.0000.1111.00<\/span><\/p>\n

int lo0<\/span><\/p>\n

\u00a0ip routing isis<\/span><\/p>\n

\u00a0ipv6 routing isis<\/span><\/p>\n

int fa0\/0<\/span><\/p>\n

\u00a0ip routing isis<\/span><\/p>\n

\u00a0ipv6 routing isis<\/span><\/p>\n

 <\/p>\n

XR Router<\/p>\n

(config)# router isis <name><\/span><\/p>\n

\u00a0net 49.0001.0000.0000.1111.00<\/span><\/p>\n

-> area: area 49.0001<\/p>\n

-> system: \u00a0.0000.0000.1111<\/p>\n

-> NSEL: \u00a0.00<\/p>\n

 <\/p>\n

\u00a0int lo0<\/span><\/p>\n

\u00a0 address-family ipv4 unicast<\/span><\/p>\n

\u00a0 address-family ipv6 unicast<\/span><\/p>\n

\u00a0int g0\/0\/0\/0<\/span><\/p>\n

\u00a0 address-family ipv4 unicast<\/span><\/p>\n

\u00a0 address-family ipv6 unicast<\/span><\/p>\n

 <\/p>\n

show clns neighbor<\/span><\/p>\n

show isis neighbor<\/span><\/p>\n

-> “L1 L2 neighbors”<\/p>\n

 <\/p>\n

IOS (Level type, interface)<\/p>\n

int e0\/0<\/span><\/p>\n

\u00a0isis circuit-type level-1<\/span><\/p>\n

 <\/p>\n

XR (Level type, interface)<\/p>\n

router isis ABC<\/span><\/p>\n

\u00a0int g0\/0\/0\/0<\/span><\/p>\n

\u00a0 circuit-type level-1<\/span><\/p>\n

 <\/p>\n

IOS (Level type, entire router)<\/p>\n

router isis<\/span><\/p>\n

\u00a0is-type level-1<\/span><\/p>\n

 <\/p>\n

XR\u00a0(Level type, entire router)<\/p>\n

router isis ABC<\/p>\n

is-type level-1<\/p>\n

 <\/p>\n

IOS (Timers)<\/p>\n

int e0\/0<\/span><\/p>\n

\u00a0isis hello-interval <sec><\/span><\/p>\n

\u00a0isis hello-multiplier <count><\/span><\/p>\n

 <\/p>\n

XR (Timers)<\/p>\n

router isis ABC<\/span><\/p>\n

\u00a0int g0\/0\/0\/0<\/span><\/p>\n

\u00a0 hello-interval <sec><\/span><\/p>\n

\u00a0 hello-multiplier <count><\/span><\/p>\n

 <\/p>\n

IOS<\/p>\n

int e0\/0<\/span><\/p>\n

\u00a0isis priority <value><\/span><\/p>\n

\u00a0 \u00a0 \u00a0-> 0 – 127<\/span><\/p>\n

\u00a0 \u00a0 \u00a0-> 64 is default<\/span><\/p>\n

\u00a0isis metric <value> [ level-1 | level-2 ]<\/span><\/p>\n

\u00a0isis password <password><\/span><\/p>\n

\u00a0isis network { point-to-point | broadcast }<\/span><\/p>\n

 <\/p>\n

Route Leaking<\/b><\/p>\n

– Routes can be leaked from Level-1 to Level-2<\/p>\n

– and visa versa<\/p>\n

 <\/p>\n

On IOS Level-1-2 Router<\/p>\n

router isis<\/span><\/p>\n

\u00a0redistribute isis ip level-2 into level-1 { distribute-list <name> | route-map <name> }<\/span><\/p>\n

access-list <number> permit | deny <protocol> <source> <wildcard> <destination> <wildcard><\/span><\/p>\n

-> network leaked – <source> <wildcard><\/p>\n

-> subnet mask to match – <destination> <wildcard><\/p>\n

 <\/p>\n

Scenario -> Leak the loopback of R3 to R1<\/p>\n

R2(config)# access-list 100 permit ip 3.3.3.3 0.0.0.0 255.255.255.255 0.0.0.0<\/span><\/p>\n

ip prefix-list ABC permit 3.3.3.3 255.255.255.255<\/span><\/p>\n

route-map LEAK<\/span><\/p>\n

\u00a0match ip add prefix-list ABC<\/span><\/p>\n

 <\/p>\n

XR<\/p>\n

(config)# router-policy POLICY1<\/span><\/p>\n

\u00a0if destination in (3.3.3.3\/32)<\/span><\/p>\n

\u00a0 pass<\/span><\/p>\n

\u00a0 end if<\/span><\/p>\n

router isis ABC<\/span><\/p>\n

\u00a0address-family ipv4<\/span><\/p>\n

\u00a0propagate level-2 into level-1 route-policy POLICY1<\/span><\/p>\n

 <\/p>\n

IOS<\/p>\n

(config)# mpls ip<\/span><\/p>\n

\u00a0mpls label protocol ldp<\/span><\/p>\n

\u00a0ip cef<\/span><\/p>\n

\u00a0int fa0\/0<\/span><\/p>\n

\u00a0 mpls ip<\/span><\/p>\n

 <\/p>\n

XR<\/p>\n

(config)# mpls ldp<\/span><\/p>\n

\u00a0int fa0\/0<\/span><\/p>\n

\u00a0int s0\/0<\/span><\/p>\n

\u00a0root<\/span><\/p>\n

\u00a0commit<\/span><\/p>\n

sh run mpls ldp<\/span><\/p>\n

 <\/p>\n

Potential Problems<\/b><\/p>\n

 <\/p>\n

Mismatched Level 1 and Level 2 interfaces<\/p>\n

Misconfigured NSAPs (NET)<\/p>\n

Duplicate system IDs<\/p>\n

Mismatched MTUs<\/p>\n

Mismatched IP addresses and subnets<\/p>\n

Mismatched topologies (single vs. multi)<\/p>\n

Mismatched metrics (narrow vs. wide)<\/p>\n

– Log Messages:<\/p>\n

– TLV contents different, code 128<\/p>\n

-> TLV 128 – IP Internal Reachability (narrow)<\/p>\n

– TLV code mismatch<\/p>\n

– TLV contents different, code 135<\/p>\n

-> TLV 135 – Extended IP Reachability (wide)<\/p>\n

 <\/p>\n

Verification (IOS):\u00a0<\/b><\/p>\n

 <\/p>\n

sh clns nei<\/span><\/p>\n

sh clns is-nei<\/span><\/p>\n

sh clns int<\/span><\/p>\n

sh isis nei<\/span><\/p>\n

sh isis spf-log<\/span><\/p>\n

sh isis database<\/span><\/p>\n

sh isis database detail<\/span><\/p>\n

-> Use to determine whether single topology or multitopolgy is configured<\/p>\n

sh isis ip topology<\/span><\/p>\n

sh isis ipv6 topology<\/span><\/p>\n

sh clns<\/span><\/p>\n

sh clns protocol<\/span><\/p>\n

-> Shows the metric types that are generated and accepted<\/p>\n

sh ip protocols<\/span><\/p>\n

sh ipv6 protocols<\/span><\/p>\n

sh isis topology<\/span><\/p>\n

sh clns nei detail<\/span><\/p>\n

sh clns int <int><\/span><\/p>\n

sh ip route isis<\/span><\/p>\n

sh ipv6 route isis<\/span><\/p>\n

 <\/p>\n

debug isis adj-packets<\/span><\/p>\n

debug isis update-packets<\/span><\/p>\n

debug spf-events<\/span><\/p>\n

 <\/p>\n

Verification (XR):<\/p>\n

 <\/p>\n

sh isis<\/span><\/p>\n

-> Shows the metric types that are generated and accepted<\/p>\n

sh isis nei<\/span><\/p>\n

sh isis int bri<\/span><\/p>\n

sh isis spf-log<\/span><\/p>\n

sh isis database<\/span><\/p>\n

sh isis database detail<\/span><\/p>\n

-> Use to determine whether single topology or multitopology is configured<\/p>\n

-> Multitopology entries:<\/p>\n

Metric: 10\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 MT (IPv6 Unicast) IPv6 2002:9:9::1\/128<\/p>\n

Metric: 10\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 MT (IPv6 Unicast) IPv6 2002:9:9:11::\/64<\/p>\n

Metric: 10\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 MT (IPv6 Unicast) IPv6 2002:9:9:18::\/64<\/p>\n

-> Singe topology entries:<\/p>\n

Metric: 10\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 IPv6 2002:9:9::1\/128<\/p>\n

Metric: 10\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 IPv6 2002:9:9:11::\/64<\/p>\n

Metric: 10\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 IPv6 2002:9:9:18::\/64<\/p>\n

 <\/p>\n

sh isis ipv4 topology<\/span><\/p>\n

sh isis ipv6 topology<\/span><\/p>\n

sh protocols<\/span><\/p>\n

sh protocols ipv6<\/span><\/p>\n

sh route isis<\/span><\/p>\n

sh route ipv6 isis<\/span><\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

IS-IS – Link state routing protocol -> 0xFEFE -> 0x0800 – Connectionless Network Protocol (CLNP) – Like an IP protocol suite in OSI model -> Router -> Intermediate System (IS) -> End host -> End System (ES) -> OSI protocol -> Directly works over layer 2 -> Integrated IS-IS can have payload of IPv4 or […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[30,9,10],"class_list":["post-213","post","type-post","status-publish","format-standard","hentry","category-ccie","tag-ccie","tag-is-is","tag-service-provider"],"_links":{"self":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/213","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=213"}],"version-history":[{"count":8,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/213\/revisions"}],"predecessor-version":[{"id":225,"href":"https:\/\/feralpacket.org\/index.php?rest_route=\/wp\/v2\/posts\/213\/revisions\/225"}],"wp:attachment":[{"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=213"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=213"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/feralpacket.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=213"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}