Aug 12, 2004 · Description of problem: tcpdump consistently reports "bad udp cksum" errors for all domain (nameserver) packets generated by the localhost, whether generated by resolver (glibc) or by named (bind), even though these packets are evidently valid (they go out on the wire and return valid responses).

May 12, 2011 · tcpdump bad udp cksum 0x431e message While troubleshooting a problem with Domain Name System (DNS) lookups on a CentOS 7 system, I ran tcpdump using the -vv option to get very verbose output. The output from tcpdump showed many "bad udp cksum 0x431b" messages. キャプチャ時にでる、UDP bad checksum エラー ( UDP checksum offload ) について 最近のNIC はNICでチェックサムを行っており、system(OS)パケットが送られた後にcheksum を行う what counld be causing bad "udp cksum" I have an Ubuntu LTS 10.04 dns server running as a guest on VMware ESXi 4.0 when I run nslookup against it I don't always get a response. After not seeing anything in the bind or system logs I ran tcpdump. Aug 09, 2018 · Hi, Recently I'm noticing an interesting issue. My CentOS servers are trying to send logs to a logging server via 514/udp, however I'm not receiving anything. I did the following on CentOS *tcpdump -vvv -nn udp -i esn160 port 514* In another session on the same server: *nc syslog-server -u 514* tcpdump started to show me messages like: *[bad udp cksum 0x3ce9 -> 0xb0f5!] Feb 19, 2019 · tcpdump udp -i vmbr0 -vv port 8089 it gives "bad udp cksum" (see below). My Influxdb server is a virtual machine on my Proxmox server 1 (see package versions below). I have tried to change the virtual network card in my Influxdb server from "virtio" to "e1000" and the bridge from vmbr0 (VLAN tagget network) to vmbr2 (not VLAN tagget) without luck. Aug 12, 2004 · Description of problem: tcpdump consistently reports "bad udp cksum" errors for all domain (nameserver) packets generated by the localhost, whether generated by resolver (glibc) or by named (bind), even though these packets are evidently valid (they go out on the wire and return valid responses). Nov 21, 2011 · Hi pjsr2, thank you for your reply. I'm not sure taht I need that, but at tcpdump bad udp cksum is not the best? I'm in a KVM environment and I found some solutions to speed up the performance with this step.

14:31:29.322429 IP (tos 0x0, ttl 1, id 53536, offset 0, flags [none], proto: UDP (17), length: 46) gw1.53493 > gw2.33477: [bad udp cksum a015!] UDP, length 18 Both sides will see this exact same packet, so I know no other modifications to the packet are happening.

Aug 12, 2004 · Description of problem: tcpdump consistently reports "bad udp cksum" errors for all domain (nameserver) packets generated by the localhost, whether generated by resolver (glibc) or by named (bind), even though these packets are evidently valid (they go out on the wire and return valid responses). Nov 21, 2011 · Hi pjsr2, thank you for your reply. I'm not sure taht I need that, but at tcpdump bad udp cksum is not the best? I'm in a KVM environment and I found some solutions to speed up the performance with this step.

# tcpdump -nvv -i bond0 multicast and port 18113 tcpdump: listening on bond0, link-type EN10MB (Ethernet), capture size 96 bytes 20:16:59.109023 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto: UDP (17), length: 61) nn.nn.nn.nn.18113 > nn.nn.nn.nn.18113: [bad udp cksum 3965!] UDP, length 33 Environment. Red Hat Enterprise Linux (Any Version)

When its applied (and it has been for a long time) dig from a linux host using UDP does not work: 15:42:17.245017 IP (tos 0x0, ttl 64, id 23959, offset 0, flags [none], proto UDP (17), length 67) 10.99.99.99.44922 > google-public-dns-a.google.com.domain: [bad udp cksum 0x2ac7 -> 0xcb1c!] 7507+ [1au] A? google.com. ar: . Bad UDP checksums are a common case in the real networking world - either due to problematic NIC's or kernel bugs/cache failures. I noticed the following behavior for the SNMP plugin in a network where bad UDP checksums occur: SNMPget telegraf.49840 > active.hostname.snmp: [bad udp cksum 0xc05f -> 0xd256!] From the service side, SYN packets come in from the client, and SYN ACK packets try to go out from the service, but they are marked as bad packets. Every single one of them! The reason is because of a bad IP header checksum where the value is 0x00 instead of being 0x5338 (for example). Am investigating a macOS Catalina machine that is believed to be infected with malware. Have been viewing packets with tcpdump and noticed, on connecting to any web address, there are legit packet