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1500 questions
14
votes
1 answer

Getting Cisco ISAKMP and IPSec SA lifetime confused

I always get confused about security association lifetime configuration on Cisco IOS. On most web-managed hardware it is clear which SA lifetime is for Phase I and which is for Phase II. On Cisco however you got this crypto isakmp policy …
Alex
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2 answers

IPv6 link-local vs unique local

When do you use link-local or unique local in IPv6 networks? (Cisco doesn't manage to explain it properly in their online material.)
Axel Kennedal
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2 answers

What is a non-portable IPv4 address block?

For example, a Whois query for 4.4.4.0 says: ADDRESSES WITHIN THIS BLOCK ARE NON-PORTABLE Does the owner simply declare the block or a subnet are not up for sale? Or does non-portable have a deeper, technical meaning? Here is the relevant section…
user2964971
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14
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6 answers

Cisco BGP - see communities on advertised-routes?

We have an outbound route-map on an eBGP peer that adds some communities to certain prefixes. Is there any way to prove that this is actually happening from the sender side in classic IOS? show ip bgp neighbor x.x.x.x advertised-routes does not show…
AnotherHowie
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1 answer

How can a TCP window size be allowed to be larger than the maximum size of an ethernet packet?

I know that TCP window sizes can be scaled to over 64KB, but looking at an ethernet packet datagram, such as this one: it looks like a layer 2 packet is limited in size to be much smaller than that. How does ACKing work at the TCP layer if a single…
Zach Smith
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14
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3 answers

What is the difference between routing table and forwarding table?

What is the difference between a routing table and a forwarding table?
Manjitha Teshara
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14
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2 answers

What are the differences in the contents of datagrams, frames, and network packets?

I'm reviewing the networking security unit of the class I'm in, and I had a question. I know that datagrams are packets at the transport layer of the OSI model, whilst frames are the name for packets in the transport layer and network packets are in…
Aditi Ramaswamy
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14
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3 answers

Is there such thing as a network bridge?

Is there such a thing as a network bridge or is it always meant as a switch implementing a bridging function? Whilst bridges are described as devices that create separate collision domains in network specifications and tutorials, I have never been…
Marcos Gonzalez
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3 answers

Where can I use the IPv6 documentation prefix

We are currently building a networking course with a practical part where students have to configure a small network in a virtual environment. However, we are not sure what ipv6 prefixes we can use for the configuration. The IPv6 documentation…
sliebald
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2 answers

What does the naming convention for Ethernet standards mean: 1000BASE-T, BASE-TX, BASE-SX, etc.? What is the meaning of the components of the name?

I understand the number in the naming convention. The number represents how many Megabits per second can the standard support. However, I do not understand the rest of the naming convention. What do "BASE," "T," "X," etc. mean? Can someone explain…
yoyo_fun
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4 answers

Is Nexus 7000 series line card "OIR" impact-free?

I have read many data sheets on the Nexus 7000 series and it's cards purporting to be capable of OIR (Online Insertion and Removal). However I have never needed to replace/reseat/add any Nexus line cards since I walked into this Nexus deployment two…
Brett Lykins
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3 answers

Should a router use SLAAC for IPv6 address assignment?

I am a little confused by the following 2 RFCs relating to IPv6: RFC 4862 (IPv6 Stateless Address Autoconfiguration) RFC 7084 (IPv6 CE Router Requirements) RFC 4862 states: The autoconfiguration process specified in this document applies only to…
banjaxed
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2 answers

Broadcasting wifi packets without a network

I have a question about Wifi, I couldn't find the answer anywhere. Is it possible to send a packet over wifi without having joined any kind of network (ad-hoc or not)? I would like to be able to send packets in the air without joining a network.…
Noé Malzieu
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4 answers

Possible (bit) patterns of a netmask

Given a prefix Y, it's easy to calculate the corresponding netmask: Put Y times a set bit, and then fill up "to the right" with zeros until one has 32 bits (IPv4) in total. Example: Prefix 24, thus netmask 11111111 11111111 11111111 00000000 or…
Daniel Jour
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7 answers

Full-duplex with two antennas

It is said that wireless is a half-duplex medium. "Dual-band" stations are now common, with one antenna in the 2.4 GHz band, and the other in the 5GHz band. Suppose now we have stations with both antennas in, say, the 5GHz band, but on different…
T. Webster
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