On Fri, Jul 8, 2011 at 12:44 AM, Anton Shterenlikht <[hidden email]> wrote: > I'm trying to troubleshoot tftpd(8). () > 192.168.232.10.15388 > buzi.tftp: [no cksum] 25 RRQ "/bsd.rd.IP32" octet ( > o > 23:25:21.024160 IP (tos 0x0, ttl 64, id 56, offset 0, flags [none], proto UDP (1 > 7), length 30, bad cksum 0 (->293a)!) > buzi.19330 > 192.168.232.10.15388: [udp sum ok] UDP, length 2 > 23:25
Hi all, currently we facing and issue when the snmp server cannot poling the certain interface info on other MX router. The traffic is flow through SRX5800 before it reach the MX router. When do tcp dump on snmp server it see "bad UDP checksum". When we do traceoption on SRX we see "bad udp length C-1 Cisco ISG RADIUS CoA Interface Guide OL-8176-01 Rev. C0 APPENDIX C Control Messages First Published: December 5, 2006 Revised: December 23, 2006, OL-8176-01 Rev. C0 Some client devices are not able to consistently get DHCP IP. Currently there is a client (MAC with e066.781e.2782) that is consistently failing to get DHCP offer packet when connected to VLAN 1020. May 24, 2019 · 14:24:01.633063 IP6 (flowlabel 0xc5ce3, hlim 64, next-header UDP (17) payload length: 105) fe80::968f:cfff:fec7:f988.dhcpv6-server > fe80::ad9a:1c99:64e3:d243.dhcpv6-client: [bad udp cksum 0x5db7 -> 0xded1!] dhcp6 reply (xid=ad3737 (status-code success) (server-ID hwaddr/time type 1 time 611849217 4c1265fa212f) (client-ID hwaddr/time type 1 Feb 03, 2005 · I configured NTP to sycn against a local server, tcpdump shows req and reply from the NTP server tcpdump-uw: listening on vmk0, link-type EN10MB (Ethernet), capture size 96 bytes 03:52:36.296738 IP (tos 0xc0, ttl 64, id 11220, offset 0, flags [none], proto UDP (17), length 76) 10.100.110.104.123 > 10.100.110.83.123: [bad udp cksum 71be!] Tcpdump Tcpdump is a commandline network analyzer tool or more technically a packet sniffer. It can be thought of as the commandline version of wireshark (only to a certain extent, since wireshark is much more powerful and capable). As a commandline tool tcpdump is quite powerful for network analysis as filter expressions can be passed Read More »
On Fri, Jul 8, 2011 at 12:44 AM, Anton Shterenlikht <[hidden email]> wrote: > I'm trying to troubleshoot tftpd(8). () > 192.168.232.10.15388 > buzi.tftp: [no cksum] 25 RRQ "/bsd.rd.IP32" octet ( > o > 23:25:21.024160 IP (tos 0x0, ttl 64, id 56, offset 0, flags [none], proto UDP (1 > 7), length 30, bad cksum 0 (->293a)!) > buzi.19330 > 192.168.232.10.15388: [udp sum ok] UDP, length 2 > 23:25
BOOTP/DHCP, Reply, length 323, xid 0x930ba16d, secs 3, Flags [none] (0x0000) Your-IP 10.0.0.2 Server-IP 10.0.0.3 Client-Ethernet-Address fa:16:3e:0e:04:32 (oui Unknown) Vendor-rfc1048 Extensions Magic Cookie 0x63825363 DHCP-Message Option 53, length 1: Offer Server-ID Option 54, length 4: 10.0.0.3 Lease-Time Option 51, length 4: 86400 RN Option In some cases the UDP checksums in packets from DHCP servers are incorrect. This is a problem for some DHCP clients that ignore packets with bad checksums. This patch inserts an iptables rule to ensure DHCP servers always send packets with correct checksums. Due to this bug DHCP offers are sometimes not accepted by Instances. Jun 17, 2008 · [tcpdump] how to fix the bad checksum problem If you capture packets using tcpdump directly from the server, your capture file may contain bad checksums. This is because your OS is currently configured to use the hardware checksum offloading feature of the NIC. # 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)
I was setting both ip and udp scum fields to 0. PKT_TX_UDP_CKSUM == PKT_TX_L4_MASK = 0x6000. I was not aware of the get_ipv4_psd_sum(ipv4_hdr); And I'm quite frankly surprised the HW doesn't already do this.
Use tcpdump to capture any UDP packets on port 8125. Use tcpdump to capture any UDP packets on port 8125. [bad udp cksum 7 c8f!] UDP, length 9. 0x0000: 4500 0025 e2f7 4000 4011 59 ce 7f 00 What I have noticed when this "stop" happens is that the entire network is flooded with TCP packed with a bad Checksum. When I examine them a number of packets have a checksum of 0X00. My neighbors are seeing the same checksum problems on their networks. Apr 06, 2015 · However, accessing the other VMs (CentOS, Debian), I get a large amount of TCP bad checksum errors. It happens with SSH, HTTP, etc. I can SSH into the FreeBSD system and then communicate with the VMs from there. Likewise, if I remote into a machine on the same LAN as the VMs, it works without errors. I haven't seen an checksum errors using ICMP. TFTP copy: operation terminated due to bad checksum comparison. I checked my settings, and noticed that when you first attempt to do the tftpdnld, you are told about some mandatory settings and some optional ones: rommon 8 > tftpdnld Missing or illegal ip address for variable IP_ADDRESS Illegal IP address.