Skip to main content
6 votes
Accepted

Can ARP tables store addresses for other networks?

"It doesn't work like that." Nothing in network A will even attempt to find network B via layer-2 (ARP), because it's not a local ("on-link") network. They will forward that ...
Ricky's user avatar
  • 32.3k
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
5 votes

Can ARP tables store addresses for other networks?

You seem to be talking about proxy ARP: the source (or previous hop) thinks that an address is on link (this might be a problem for you). On-link addresses are resolved by ARP, so an ARP request is ...
Zac67's user avatar
  • 85.5k
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
  • 85.5k
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
  • 17.4k
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

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
  • 19.7k
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
  • 13.4k
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
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

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
  • 85.5k
3 votes
Accepted

STP related question

Disabling STP and creating a loop will crash the network with a broadcast storm. STP was designed to prevent layer-2 loops by enabling a single loop-free path to the root bridge. STP is communicated ...
Ron Maupin's user avatar
  • 99.9k
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
  • 85.5k
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
  • 85.5k
2 votes
Accepted

How do layer 2 switches route based on MAC when daisy-chained?

Switches are self-learning bridges: they inspect each incoming frame for its source MAC address and store that address with the ingress port in their source-address or MAC table. Any MAC address can ...
Zac67's user avatar
  • 85.5k
2 votes

IPv6 subnetting with different end device requirements

Just use a /64 for every network, don't overthink it. And with a /48 you have more than enough /64's to use one for every network and use one /64 to split into /127's for point to point links. If you ...
Teun Vink's user avatar
  • 17.4k
2 votes

must an IPv6 router have an IP address in the SLAAC prefixes it's advertising?

Technically, there's no requirement for a prefix to be bound to the interface. The RA will be sent from the lladdr, and nodes will build routes using that lladdr as the destination. NDP ("arp&...
Ricky's user avatar
  • 32.3k
2 votes
Accepted

must an IPv6 router have an IP address in the SLAAC prefixes it's advertising?

Unless you apply an address in a prefix for that link, the router has no way to know that is the prefix for that link, so it cannot route packets destined to that network to that interface. A host (a ...
Ron Maupin's user avatar
  • 99.9k
2 votes

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

I was going through this feature of GRE called GRE-in-UDP encapsulation. The RFC says it is unidirectional and the tunnel traffic is not expected to be returned back to the UDP source port values used ...
Mike Pennington's user avatar
2 votes
Accepted

Is route from traceroute guaranteed to match the route packets will take in actual usecase?

The packets are first being sent to the other side of the country instead of immediately being sent to nearby city and then to the server in question. That is quite possible, especially when an ISP ...
Zac67's user avatar
  • 85.5k
2 votes

Geolocation specific ASN

ASNs aren’t bound to a specific location, so what you’re asking is impossible to answer in general. Some large networks may use an ASN for a specific region, but if that’s the case you can only find ...
Teun Vink's user avatar
  • 17.4k
2 votes

which protocol is invoked first by routers ? routing (routing table) or ARP?

The routing (or forwarding) table is not a protocol. It's a mechanism to implement the network layer function(s). In order to route an IP packet, you first need to know which interface you will be ...
Ron Trunk's user avatar
  • 67.7k
2 votes
Accepted

Why MLS2 Doesn't Get ICMP Packet To Where It Should?

We're missing a bunch of output here, but here is a working theory: PC1 (which is in VLAN 10) has a default gateway of 10.10.0.11 (MLS1). Due to Per-VLAN Spanning Tree Protocol (PVSTP+) blocking the ...
Angelos Vassiliou's user avatar
2 votes
Accepted

Computers on different subnets can't talk to each other

You need to either remove the routers, connect all clients to the switches directly, use a single, shared subnet (e.g. 192.168.1.0/24) or use a distinct, non-overlapping subnet off of each router and ...
Zac67's user avatar
  • 85.5k
2 votes

How does the final next-hop router forward a frame to the destination device if the public IP address is that of its router

how does it know which device on its network to forward the query to? Without explicit, additional setup it doesn't. Forwarding a packet with a public IPv4 destination to a server with a private ...
Zac67's user avatar
  • 85.5k
2 votes
Accepted

Is the routing table a control plane concept or a data plane concept?

The effective routing table or forwarding information base FIB is part of the data or forwarding plane. The control plane keeps a more detailed routing information base RIB that is used for exchanging ...
Zac67's user avatar
  • 85.5k
1 vote

2 Routers for PPPoE and NAT 5 Public IP

The primary router's LAN interface connected to the WAN interface of the secondary router. That won't work. The primary router's LAN subnet doesn't match the secondary router's WAN IP. The public WAN ...
Zac67's user avatar
  • 85.5k
1 vote

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?

inside a packet there is information about the sender's public IP and MAC and the receiver's public IP and MAC An (IP) packet header stores the sender's IP address (public or private, possibly ...
Zac67's user avatar
  • 85.5k
1 vote

Rip Routing Protocol

A routing protocol like RIP helps create a routing table that is used to make routing decisions. For R1 and R4 that is trivial, but R2 and R3 need to decide which interface to use. R2 learns from R3 ...
Zac67's user avatar
  • 85.5k

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