Questions tagged [is-is]
For questions about the Intermediate System to Intermediate System (IS-IS) routing protocol.
32
questions
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2
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37
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removing ip proxy-arp
I would like to understand from experts here what could be potential things that can go wrong of disabling ip proxy-arp
- 57
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1
answer
63
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Different BGP attributes that can be used for advertise
What are different BGP attributes can be used to advertise prefixes?
- 57
3
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1
answer
93
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Should I be using point-to-point or broadcast if I plan on using SVIs in IS-IS on Juniper?
Apologies in advance if this is super-basic question, still learning ISIS.
I'm migrating from Cisco over to Juniper in an environment where all of the switches are running EIGRP, are on a 172.31.255.0/...
- 33
0
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1
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58
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Does BGP protocol is required to run IS-IS Segment Routing?
In order to do IS-IS segment routing, do I need to run BGP on routers? Lets say, I have R1-R2-R3-R4 topology. In this topology, I will configure IS-IS segment routing on all routers. My question is do ...
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1
answer
175
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Why is OSPF more popular than IS-IS in enterprise networks? [closed]
I've read that IS-IS is more popular than OSPF in Internet Service Providers due to historical reasons (mainly that initially IS-IS had better hardware support and wasn't for IP only).
But why did ...
1
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1
answer
537
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BGP "protocol next hop" resolves to different next-hop address than the same IP using ISIS
I have a BGP-learned prefix 130.130.0.0/24 with protocol next hop 10.0.2.5:
root@r2> show route 130.130.0.0 detail
inet.0: 60 destinations, 61 routes (57 active, 0 holddown, 4 hidden)
130.130.0.0/...
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2
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1
answer
273
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How does ISIS find a next hop address for a prefix learned by ISIS?
I have two Juniper routers connected like this:
r1[ge-0/0/2] <-> [ge-0/0/3]r2
Both ge-0/0/2 in r1 and ge-0/0/3 in r2 do not have a family inet configured:
root@r1> show interfaces ge-0/0/2 ...
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0
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1
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1k
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isis redistribute bgp not working
I am having trouble getting route redistribution into ISIS working. It works from ISIS to BGP, but I can't get the opposite to show up. I am using IOS-XR
Network has 3 routers:
A----B----C
A and B ...
- 108
1
vote
0
answers
17
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Can BGP-LS provide an ip address as a node attribute when distributing IS-IS
I have an IS-IS network (all cisco) with a BGP router (cisco) that I am using to distribute the network link-state for monitoring / analysis. one thing I would like is to receive an IP address for ...
- 108
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2
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845
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Understanding the IS-IS wide metric style for Traffic Engineering in Juniper MX
Can someone please explain why do we need to enable 'wide-metric' for IS-IS if we are going to enable MPLS Traffic engineering on Juniper MX routers?
I mean what does traffic engineering has to do ...
- 1,110
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116
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IS-IS as a PE-CE routing protocol [closed]
In case of IS-IS as a PE-CE routing protocol for MPLS VPNs , when route is redistributed from BGP to IS-IS , does 'Down Bit' is also set to avoid routing loops?.
Background Information
We know that ...
- 1,110
0
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1
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1k
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IS-IS Interface Metric/Cost Calculation Issue in Juniper MX
I am facing a very strange issue with regard to IS-IS Interface Metric / Cost calculation in Juniper MX. We have configured a reference bandwidth of 1000G on all routers.This by definition means an ae ...
- 1,110
-1
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1
answer
1k
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How to implement Layer 3 (OSPF, IS-IS) link redundancy?
I think this kind of topic may be a course basic, but I'm still have a lot of technical doubts on how to implement redundant links on Layer 3, for example:
-In order to use dual homing for a remote ...
1
vote
1
answer
455
views
What is the difference between ISIS neighborship and adjacency?
Is there a difference between neighborship and adjacency in case os IS-IS? Many times I come across both the words in the context of IS-IS. Do they have different meanings based on the IS-IS states?
- 345
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1
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2k
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How many maximum number of ISIS routers can be in an area or level?
As far as OSPF, I know that Cisco recommends that you should not have an OSPF area with more than 90-100 routers. Is there such restriction or recommendation for ISIS areas or levels?
- 345
4
votes
1
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679
views
Does LDP not generate a label for default route for ISIS Level 2?
LDP generates local bindings for all the routes in the routing table. I configured an ISIS topology such that:
R1 ----- R2 ----- R3 ----- R4 ----- R5
L1 L1/2 L2 L1/2 L1
...
- 345
4
votes
2
answers
441
views
In Multi Area IS-IS how does an L1 router choose the L1/L2 to use for interarea routing?
This is related to a similar question IS-IS multi area But instead of the how is the destination router chosen, I want to know how L1 routers choose the first L1/L2 router.
Using the below topology:
...
- 108
2
votes
1
answer
131
views
What happened if I set up multiple links between an IS to other IS?
I don't have machines to test this yet. But I would like to ask what would happened if I set up multiple links between an IS to other IS?
Something like this one:
-- --Link 1-- --
--- |R1| --...
- 656
1
vote
0
answers
486
views
Problem configuring L3VPN with MPLS, RSVP-TE, VLAN
We are having problems to configure a L3VPN in VIRL with an MPLS CORE NETWORK that uses RSVP-TE as label exchange protocol and IS-IS as IGP protocol. The idea is to distinguish different type of ...
1
vote
4
answers
195
views
IS-IS IPv6 over IPv4
In IS-IS the router knows the interfaces addresses of the other routers. So would it be possible to connect two IPv6 areas over an IPv4 area?
A router in area A knows that the destination ipv6 ...
- 97
1
vote
2
answers
976
views
Regarding clns mtu
I understand the below points,please confirm if my understanding is correct.
MTU > MSS
E.g if my MSS is 1460 bytes, then MTU should be at least 1500 bytes(20 bytes for IP header and 20 bytes for TCP ...
- 893
1
vote
2
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6k
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Understanding route metric 0
I have the below output from an IOS-XR box:
RP/0/RSP0/CPU0:RTR1#show route 10.10.10.10
Wed Mar 27 13:34:52.553 IST
Routing entry for 10.10.10.10/32
Known via "isis IGP", distance 115, metric 261, ...
- 893
1
vote
0
answers
75
views
Policy routing with IS-IS
three routers are connected where
Router A connected to router B
A (gig0/0/0 ip address 10.10.1.1)====> B(gig0/0/0 ip address 10.10.1.2
A(gig0/0/0=> ip address 10.11.1.1===>B(gig0/0/...
2
votes
1
answer
764
views
ISIS Max metric
I need to confirm the below as i don't have access to a lab.
I have 4 XR boxes connected linearly as shown.Router A is advertsing PC subnet in isis.
My understanding:
So when the subnet of PC A ...
- 893
1
vote
3
answers
4k
views
How to enable isis in packettracer
I am using cisco packet tracer 7.0. I am supposed to set isis as the routing protocol. But when try to do this in config mode, the router does not identify the command "router isis".
When I enter ...
- 13
1
vote
2
answers
336
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Does the Shortest Path First algorithm (SPF) Algorithm for OSPF and IS-IS generate all shortest paths between nodes, or just one?
To be more specific. If there are two equal cost paths between two nodes, does the SPF Algorithm give the next hop value for both paths?
- 11
4
votes
2
answers
320
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IS-IS multi-area
It is well known that an IS-IS L1 router chooses the nearest L1/L2 router to route inter-area traffic, if there is no route leaking as defined in RFC 2966.
However, providing that there is no route ...
- 47
1
vote
2
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395
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IS-IS Hello packets and IPv4/IPv6 addresses
IS-IS Hello packets contain IPv4(and IPv6 address). For example see the "IPv4 Interface" field in this IS-IS Hello packet:
$ tcpdump -c1 -vvvr isis.pcap
reading from file isis.pcap, link-type EN10MB (...
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1
vote
1
answer
1k
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MPLS load balancing on Huawei S5700
On a L3 switch there are two equal cost ISIS routes.
Destination/Mask Proto Pre Cost Flags NextHop Interface
10.150.4.12/32 ISIS-L2 15 10 D 10.200.15.42 Vlanif27
...
- 69
6
votes
1
answer
674
views
Juniper IS-IS levels hierarchy configuration
Can someone please tell me what is the interface ge-2/1/0.0 IS-IS level after we have applied this config?
Does Juniper takes both commands?
level 2 disable at the interface level
level 1 disable ...
- 91
3
votes
2
answers
5k
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How does IS-IS carry IP routes?
IS-IS runs natively on layer 2 of the OSI reference model. How will the routing be done in that?
My doubt is that layer 3 has the ability to do the routing. But, ISIS does not run in layer 3 rather ...
- 1,398
4
votes
1
answer
2k
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Cisco & Juniper: IPv6 link-local addresses used between ISIS neighbours
I am configuring IPv6 between a Juniper MX80 and Cisco 7206VXR which already happily run IPv4 over ISIS and iBGP.
ISIS is carrying IPv6 routes between the two devices but I have what I believe is a ...
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