Network Engineering Stack Exchange Community Digest

Top new questions this week:

How to restrict routes redistributed into ISIS in IOS XR?

I have a router running Cisco IOS XR with established L2 ISIS adjacency with a neighbor router. I would like to inject only the IPv4 address configured on loopback interface into the ISIS. The route ...

cisco-ios-xr route-filter  
asked by Martin 4 votes
answered by Martin 4 votes

Does Cisco CSR 1000v have a management interface?

According to Mapping Cisco CSR 1000v Network Interfaces to VM Network Interfaces document, the newer CSR 1000v routers no longer have the dedicated management interface Gi0: In Cisco IOS XE Release 3....

asked by Martin 3 votes
answered by Marc 'netztier' Luethi 3 votes

Why test routing policy do not match in vMX?

This is my routing-policy: policy-statement rp-add-as-path-3times-local-as { term prefix1 { from { route-filter orlonger; } then { as-...

asked by 244boy 3 votes
answered by Jordan Head 3 votes

SFP+ 10GBASE-LR and attenuator

This picture is a part of the Intel E10GSFPLR (SFP+, Long Reach) datasheet. Can I use them in a short link (less than 1 meter) without any attenuator? Which numbers are important in this datasheet to ...

fiber sfp optics 10gbase  
asked by A.A 2 votes
answered by Zac67 3 votes

Under what circumstances is the ARP table updated?

Lets say we have 3 devices in the same shared medium : A, B and C. A wants to send a message to B, so before, it sends an ARP request as a broadcast message. When B receives it, it will update its ARP ...

mac-address arp  
asked by shaymin shaymin 1 vote
answered by Ron Maupin 0 votes

Do layer 2 protocols allow hosts to communicate without being on a network?

Please go easy on me as I'm just a noob in the networking space. As far as I have learnt, layer 2 protocols use MAC addresses for communication, which doesn't really depend on what network you're in ...

mac-address layer2 osi  
asked by Vivek Yadav 1 vote
answered by Zac67 4 votes

Greatest hits from previous weeks:

PING port number?

Yesterday interviewer ask me what is port number for ping and which protocol ping use TCP/UDP. After interview I search on internet and found different results someone says ICMP uses Port 7, someone ...

tcp ping udp icmp  
asked by Nishad Morey 65 votes
answered by Jens Link 92 votes

Is Ethernet port blinking really useful?

This question may not look as an important one and in fact it is just out of curiosity. But to the point: Is Ethernet port blinking really useful? Ethernet ports usually have two light indicators ...

ethernet hardware  
asked by Stanowczo 45 votes
answered by Zac67 63 votes

Difference between Subnet and VLAN?

You often hear the terms Subnet and VLAN used interchangeably. With the ubiquitous nature of IP these days, when are the two not considered roughly the same from a high-level, understanding that ...

ipv4 vlan subnet  
asked by generalnetworkerror 37 votes
answered by ytti 45 votes

How does a switch learn a switch table?

Say the switch table is empty. If computer A sends a frame destined to computer B, the switch will broadcast asking who has the mac address of B. What if C suddenly sends a frame to A? What is the ...

switch ethernet mac-address arp  
asked by Celeritas 24 votes
answered by Ron Trunk 42 votes

What can cause "FastEthernet is up, line protocol is down" on a Cisco Switch?

I wonder what can cause the first line output of the command show interfaces to be: FastEthernet is up, line protocol is down. In other words, Is the cable that is connected to the local interface, ...

cisco switch ethernet interface  
asked by kolxxx 10 votes
answered by Mike Pennington 13 votes

What is real difference between host and node in network

According to wikipedia host is A network host is a computer or other device connected to a computer network. A network host may offer information resources, services, and applications to users or ...

lan network-access  
asked by apm 19 votes
answered by Eddie 23 votes

RSTP vs. STP it really sounds just a big ball of semantics? what's the main difference between them?

one difference is that Rapid Spanning Tree Protocol (RSTP IEEE 802.1W) assumes the three Spanning Tree Protocol (STP) ports states Listening, Blocking, and Disabled are same (these states do not ...

asked by user7741 8 votes
answered by APA 11 votes
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