11
votes
Accepted
dont fragment bit PING TOOL
Running "ping -M do -s 1490 example.com" says that the ICMP data size is 1490 bytes and fragmentation is not allowed. For this size of ICMP data, ICMP size (i.e., header + data) is 1498 bytes. Adding ...
- 153
11
votes
Cumulus Linux and Whitebox switch hardware?
Disclaimer: I work at Cumulus Networks
To address a few of the high level points/concerns raised:
1.) Is ONIE getting traction?
ONIE is the de facto method for getting software onto whitebox ...
- 111
11
votes
Accepted
Difference between Linux Bridge and Open vSwitch
Open vSwitch has a section on that in their FAQ:
Q: Why would I use Open vSwitch instead of the Linux bridge?
A: Open vSwitch is specially designed to make it easier to manage VM network ...
- 1,949
11
votes
Accepted
What is the difference between tshark, dumpcap and others for collecting/sniffing traffic?
Wireshark is a graphical application. tshark is that application without the GUI. (i.e. command line.) dumpcap, per Wireshark's documentation, is "a small program whose only purpose is to capture ...
- 31.1k
9
votes
net-snmp Creating my own MIB: No Such Instance currently exists at this OID
I think your issue is coming from a simple misconception of how SNMP data (OIDs) is structured, and how snmpwalk, snmpget, and snmpgetnext interact with it.
SNMP organizes the OIDs into related ...
- 6,925
7
votes
Cumulus Linux and Whitebox switch hardware?
is it reasonable to suggest that the relatively low mind share and vendor presence is a potential operational risk?
There is the potential for both risks and rewards with choosing such a solution. ...
- 27.1k
6
votes
how to find the right value of MTU Jumbo frame
Make sure there's a notable performance difference between jumbos and standard frames - without it, there's little reason to dive in. Hardware offloading tends to make jumbos obsolete unless you need ...
- 79.8k
5
votes
Accepted
Difference between Switch and Linux Bridge
The three major differences between a managed switch and using Linux bridge interfaces are performance, port density, and features.
Most managed switches will embed some of their programmed ...
- 27.1k
5
votes
Accepted
How can I get these static IPv4 routes to work?
Step one, enable IP Forwarding on node2 and node3 (or the nodes will be "hosts" not "routers")
All the nodes need to know what isn't directly attached:
Node1
ip route add 10.1.1.0/24 via 10.1.3.3
...
- 31.1k
5
votes
What will happen at server side if it received 2 SYN packet from the same client application?
Basically, a TCP receiving duplicate SYNs will SYN,ACK them, but it will receive a RST for the duplicate.
RFC 793, Transmission Control Protocol, Section 3.4. Establishing a connection explains ...
- 97.7k
5
votes
Forward Avahi mDNS packets from one network to another
Zeroconf Networking RFC 6272, RFC 6273 has the fundamental design constraint of being "local subnet only".
Zeroconf's multicast packets have a TTL of 255, and if you try forward these ...
- 8,410
4
votes
Accepted
Cumulus Linux and Whitebox switch hardware?
is it reasonable to suggest that the relatively low mind share and vendor presence is a potential operational risk?
This is always an issue. Products from a small vendor could (and more often than ...
- 31.1k
4
votes
Accepted
Access a Palo Alto VPN using Mint
The thing is that you are not using the official Global Protect client so you need and extra configuration step in the firewall. You need to define X-Auth support (on the firewall) and all related ...
- 1,152
4
votes
Is the Nth ports on 127.0.0.1 and 127.0.0.2 same ?
Can I use the same port numbers for both but binding one of them to
127.0.0.1:N and the other to 127.0.0.2:N ?
Yes, you can use the same port number on two different 127.X.X.X addresses.
Are ...
- 1,636
4
votes
Calculated window size in Wireshark
This post has a good explanation for what you're seeing.
What you see is normal behavior. Both sides send a small window size
and neither announce that they are able to use window scaling. So in
...
- 2,337
4
votes
What are entries in kernel IP table?
What route -n (or netstat -rn) is showing you needs a bit of interpretation - a "gateway" of 0.0.0.0 means that the next hop for any packet sent to this subnet is the actual destination host, not a ...
- 508
4
votes
Accepted
Understanding Linux Bridging
The way switches (bridges) work is that a switch builds a MAC address table which relates MAC addresses to the port(s) where the MAC addresses are connected. When a frame comes into a switch port, the ...
- 97.7k
4
votes
Accepted
TCP Client-Server with mtu is set, Issue with fragmented packets
You are confusing MTU and MSS.
The MTU 1500 is related to ethernet, so it includes the IP and TCP headers.
Both have a minimum size of 20, so the MSS (maximum segment size) for TCP is in this case ...
- 19.3k
4
votes
Accepted
What could cause kvm virtualized pfsense to get 84mbps behind physical pfsense, but then drop to 1mbps when it replaces physical pfsense?
JFL was correct it was a NIC checksum offloading error. My guess is that when my virtual router was behind my physical router it somehow made it so it didn't need to do checksumming.
Recap of ...
- 287
4
votes
Accepted
How do I find the IP of the DNS server that respond for a specific domain name?
The authoritative name server should be in the domain's NS record.
In Windows, this can be looked up
nslookup -type=ns somedomain.com
In Linux, something like
dig somedomain.com NS +noall +answer
...
- 79.8k
4
votes
Accepted
tcpdump output with bad length indicator present
The 1472 is the maximum payload length for the UDP datagram. The 1500 is the MTU (maximum packet size), from which you must subtract the IP header length (20 for IPv4) and the UDP header length (8), ...
- 97.7k
4
votes
Inconsistent behavior of link aggregation
It depends on the LACP load balancing algorithm. The LACP load balancing algorithm is only locally significant (they don't have to match on Mellanox and Arista switch).
Load balancing algorithms are ...
- 108
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 ...
- 16.6k
3
votes
Difference between Switch and Linux Bridge
The linux bridge is a pure software switch -- the cpu is involved with every packet. With a "managed switched", there will be dedicated switching hardware.
- 31.1k
3
votes
Accepted
Will Linux send the ARP gratuitous or ARP probe (defined in RFC 5227)
Manually configuring an IP address on a device doesn't require the device to check for address conflicts. It is only if the device configures its own IP address (DHCP, etc.) that it should check for ...
- 97.7k
3
votes
Force10 port channel to server that also supports PXE boot
@Matthew you are on the right way. I have faced this exact problem in the past and I have used this command in S4810 devices.
Unfortunately, I suspect this command is not supported in all Force10 ...
- 1,152
3
votes
Removing directly connected route from routing table in Linux
The connected route is generated automatically by the kernel from the prefix length (or netmask) associated with the interface. In order to avoid the connected route, you need to set a prefix length ...
- 400
3
votes
dont fragment bit PING TOOL
When you specify "-s 1490" you set size of ICMP packet to 1490 bytes. Then the IP stack of your system adds ICMP and IP headers which equals to 28 bytes. So in this case while specifying size of 1490 ...
3
votes
Accepted
iwconfig Tw-power value signification
The Tx-Power value is represented in dBm. This is a relative measure, specifically dB relative to a milliWatt. Wikipedia has a good page on dBm that covers the formulas to covert this to actual power ...
- 27.1k
Only top scored, non community-wiki answers of a minimum length are eligible