Hot answers tagged

9 votes
Accepted

When would we want to do traffic steering?

One example would be when the 'best path' is not actually desirable for the traffic in question. The selected path might be the most efficient (shortest in terms of routed hops etc.) but might ...
FrameHowitzer's user avatar
6 votes
Accepted

Do Directly Connected Routers Need Routing Protocols For DHCP Relay To Work?

Routers need to know how to reach networks in order to send packets to those networks. DHCP relay is sending packets to other networks. Routers learn routes in three ways: Directly connected networks ...
Ron Maupin's user avatar
  • 99.4k
6 votes

How Network layer routing actually works in the physical world

I want to make a few clarifications to @Effie 's answer: The basic idea for this separation, is that each autonomous system can choose how to arrange routing within itself, however routing between ...
Ron Trunk's user avatar
  • 67.3k
5 votes
Accepted

How Network layer routing actually works in the physical world

I guess this question will require several iterations, so here is iteration 1 Basically, Internet consists of individual networks. Each network belongs to some organization/enterprise/other kind of (...
Effie's user avatar
  • 1,828
5 votes
Accepted

Can LACP connect to 2 different firewalls?

Can LACP be set up to connect to two different firewalls? If LSW-1 and LSW-2 are indeed multi chassis LACP capable (Stack, Stackwise, M-LAG, multichassis LACP, VPC, VSS ... feature names vary by ...
Marc 'netztier' Luethi's user avatar
4 votes

In router's config, why do I need to advertise the directly connected network?

I think you misunderstand the OSPF and EIGRP network statement. The network statement does not advertise a network, it tells the routing protocol which interface(s) to include in the routing protocol ...
Ron Maupin's user avatar
  • 99.4k
4 votes
Accepted

Static route is not saved - Why?

On ISP1, you have configured 209.165.240.13/30 on interface Serial0/1/0. That interface doesn't seem to be up or even exist (see routing table), so the static route via 209.165.240.14 cannot become ...
Zac67's user avatar
  • 83.9k
4 votes
Accepted

What's the reasoning behind the "Longest prefix match" algorithm?

Would any problems occur it it chose one of the less-specific routes? Yes. Your PC is a good example. You (usually) have two routes in your PC's routing table. It will look something like this: ...
Ron Trunk's user avatar
  • 67.3k
4 votes
Accepted

Allow active connections in firewall on multiple BGP connected routers

As you figured out, doing stateful firewalling on external links doesn't work well if you're multihomed. Typically, you either do stateless firewalling on external links, or place the firewall behind ...
Teun Vink's user avatar
  • 17.1k
4 votes

Can LACP connect to 2 different firewalls?

Generally, LACP does not support grouping links from multiple chassis. LACP works between two entities, not more. However, there are proprietary stacking solutions that combine multiple physical ...
Zac67's user avatar
  • 83.9k
4 votes

In a trace route, do routers that do not respond still forward the packets?

Answering ICMP requests sent to the router is a function typically performed by a router's management plane. Replying to ICMP (and at what rate) is optional. Forwarding packets is done by the ...
Teun Vink's user avatar
  • 17.1k
3 votes
Accepted

Confused about the BGP ConnectRetryTimer

Mis-configuration of 2 peers that are able to otherwise communicate will usually not result in Idle state. The most common cause for Idle state would be one-way communication or timeout due to ...
FrameHowitzer's user avatar
3 votes
Accepted

Routing table updates Limits

but the routers on the internet don't have entry for every other destination network on the internet right ? In fact, many routers on the Internet DO have all entries. The size of the Internet IPv4 ...
Ron Trunk's user avatar
  • 67.3k
3 votes
Accepted

Is internal network traffic sent to private subnets via their NAT Server?

Is internal network traffic sent to private subnets via their NAT Server? Internal traffic should never be NATted. NAT is a necessary translation between incompatible addressing schemes like sending ...
Zac67's user avatar
  • 83.9k
3 votes
Accepted

Why do typical spine-leaf architectures have one border leaf instead of all leafs having an uplink?

Typically, connections to the WAN/Internet are done by routers. Connecting every leaf in your network to a set of routers would require routers with LOTS of ports, and the price per port on routers is ...
Teun Vink's user avatar
  • 17.1k
3 votes
Accepted

Are there any methods of differentiate between a single computer and a NAT router?

IPv4 (OSI network layer) addresses have no distinguishing attributes that would differentiate them between single devices and NAT Devices Assumptions (summarized from OP): Conclusions No network ...
generalnetworkerror's user avatar
3 votes
Accepted

Multiple hosts with same ip/subnet seperated by router possible?

You cannot have the same IP network on different layer 3 interfaces of the same gateway device (router or layer 3 switch, firewall, etc.) without the use of a feature like VRF to logically segment the ...
FrameHowitzer's user avatar
3 votes
Accepted

Import route from one rip group to another

RIP Groups aren't routing-tables - think of them as a way to group connection-specific information (like different authentication types or export policies) for different sets of neighbours. If all ...
Benjamin Dale's user avatar
3 votes

If the destination MAC is changed every hop. When it arrives at the destination router, how will it know which device to deliver the packet to?

This is the role of the ARP protocol: find the MAC associated with the IP address we want to talk to. Assuming MAC-based network (not all networks use MAC addresses) When receiving a packet a router ...
JFL's user avatar
  • 19.6k
3 votes

Who/What is AS4100000000?

BGPView [1] has it listed as an Austrian company EDV Consulting Zoichter GmbH, but this may also be a glitch in the reporting output owing to it not having a registry entry and reprinting the prior ...
Benjamin Dale's user avatar
3 votes
Accepted

what is the purpose of GRE in UDP encapsulation if its unidirectional

The use case is passing flow hashes from the overlay network to the underlay network. Higher level protocols generally don't like to have their packets reordered, it makes stream reassembly and ...
Peter Green's user avatar
  • 13.3k
2 votes

Tracing a route, from 127.0.0.1 through my network to 20.43.161.105

Are their any setting to force the tracert to report the whole IPV4 route? Tracert/traceroute work by sending probe packets (usually ICMP echo requests) with increasing TTL values and reporting the ...
Zac67's user avatar
  • 83.9k
2 votes
Accepted

how do 2 different network communicate with each other

You are referring to the NAPT variant of NAT. In such a case, you must have NAPT port forwarding configured on the NAPT router. You cannot directly connect to a private address across the public ...
Ron Maupin's user avatar
  • 99.4k
2 votes

Can multiple LANs be configured to work as one when connected together?

If you connect two LANs via bridge/switch they become one LAN or broadcast domain. You can run the hosts in different subnets but that won't work with the usual DHCP setup - multiple DHCP servers ...
Zac67's user avatar
  • 83.9k
2 votes

What's the reasoning behind the "Longest prefix match" algorithm?

The longest-prefix-preferred rule saves you the hassle to finely split up all routing into distinct routes (if no overlap would be allowed) and use a coarser, "catch-all" route instead. A ...
Zac67's user avatar
  • 83.9k
2 votes

In router's config, why do I need to advertise the directly connected network?

I don't understand, how can I have an interface which I don't connect? Interfaces that are connected to hosts (PCs) don't have any routers connected and therefore don't need to send hellos. Also, in ...
Ron Trunk's user avatar
  • 67.3k
2 votes
Accepted

Why No Ping When Use Static and RIP in This Network?

You are not actually running RIP since only one router is running RIP. RIP will exchange routing information with other RIP routers, but a single router running a routing protocol cannot exchange ...
Ron Maupin's user avatar
  • 99.4k
2 votes
Accepted

Can control plane and data plane be different in BGP?

How can the data path and control path be different in BGP-based routing? I think there's a misunderstanding. BGP is run by the control plane. The control plane then decides which routes are actually ...
Zac67's user avatar
  • 83.9k
2 votes
Accepted

Trying to achieve ECHO request reaching destination in other VLAN

It's almost impossible to tell without information such as VLAN and spanning tree status information on each switch, etc. but I would guess from a quick glance that you have problems between the ...
FrameHowitzer's user avatar
2 votes

Trying to achieve ECHO request reaching destination in other VLAN

The VLANs need to be created on the L3 switch. The gateway IP addresses must be configured on the L3 switch, on each VLAN interface/SVI. IP addresses on an L2 switch are for management only - usually ...
Zac67's user avatar
  • 83.9k

Only top scored, non community-wiki answers of a minimum length are eligible