Re: Does the debian kernel sends the gratuitous arp ?
On Mon, Oct 09, 2023 at 10:15:38PM +0200, Geert Stappers wrote: > On Mon, Oct 09, 2023 at 08:39:02PM +0530, Balaji G wrote: > > Hi Geert, > > Hello mailinglist (archive )readers of debian-user@lists.debian.org > Hello again, > > > >>> During `ip link set down dev eno5np0` and `ip link set up dev eno5np0` > > >>> are NO IP-addresses involved. > > > > This interface eno5np0 is configured with the ip addresses(10.45.10.4 ). > > > > # ifconfig > }( mismatch between `ifconfig` command expected `ifconfig` output ) > > eno5np0: flags=4163 mtu 1500 > > inet 10.45.10.4 netmask 255.255.255.0 broadcast 10.45.10.255 > > ether 88:e9:a4:49:18:48 txqueuelen 1000 (Ethernet) > > RX packets 2967346895 bytes 4417546189260 (4.0 TiB) > > RX errors 0 dropped 1 overruns 0 frame 0 > > TX packets 1634521866 bytes 2220475762246 (2.0 TiB) > > TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 > > > I did missed "LOWER_UP", then I noticed that `ifconfig` is used. More > on that later. Back to 'Subject: Re: Does the debian kernel sends the > gratuitous arp ?' > > To me is the answer "Yes, Debian kernel sends gratuitous ARP when it > supposed to do". But we, this mailinglist, have this discussion because > somewhere is the gratuitous ARP missing. What triggered the "I wonder > why there is no gratuitous ARP?" is yet unknown. > > Let me try to capture a gratuitous ARP. I will be using only one > interface (it is OK if the computer has many other network interfaces) > Using two logins as root, one for "tcpdump", the other "set address". > > In "tcpdump session" > > tcpdump -n -i eth0 arp > > > In "set address session" > > sudo ip address add 198.51.100.23/24 dev eth0 > > > Back to "tcpdump session". > > And to my surprise: **no** gratuitous ARP ! > > It should be there. I even tried after: > > $ cat /proc/sys/net/ipv4/conf/eth0/arp_notify > 0 > $ echo 1 | sudo tee -a /proc/sys/net/ipv4/conf/eth0/arp_notify > 1 > $ cat /proc/sys/net/ipv4/conf/eth0/arp_notify > 1 > $ > > > I'm gonna sleep about it. Expect me back over 48 hours. :-) > > Thanks, > > Yeah, thanks for the good question. > It did learn me that things have changes. I hope it is the improvement that was aimed for. No, I have no idea if the H.A., High Available, setup I did build for a previous employer are effected. > > Balaji > > Groeten > Geert Stappers > > > About ifconfig : > > https://serverfault.com/questions/633087/where-is-the-statement-of-deprecation-of-ifconfig-on-linux > a.k.a. use `ip addres`, `ip a` for short. Groeten Geert Stappers -- Silence is hard to parse
Re: Does the debian kernel sends the gratuitous arp ?
Hi Groeten, The IP address is already assigned to this interface device eno5np0. Please find my reply mail below. Thanks, Balaji On Mon, 9 Oct 2023 at 20:39, Balaji G wrote: > Hi Geert, > > >>> During `ip link set down dev eno5np0` and `ip link set up dev eno5np0` > > > are NO IP-addresses involved. > > This interface eno5np0 is configured with the ip addresses(10.45.10.4 ). > > # ifconfig > > eno5np0: flags=4163 mtu 1500 > inet 10.45.10.4 netmask 255.255.255.0 broadcast 10.45.10.255 > ether 88:e9:a4:49:18:48 txqueuelen 1000 (Ethernet) > RX packets 2967346895 bytes 4417546189260 (4.0 TiB) > RX errors 0 dropped 1 overruns 0 frame 0 > TX packets 1634521866 bytes 2220475762246 (2.0 TiB) > TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 > > > > Thanks, > > Balaji > > > > On Sun, 8 Oct 2023 at 20:58, Jeffrey Walton wrote: > >> On Sun, Oct 8, 2023 at 4:58 AM Geert Stappers >> wrote: >> > >> > On Sun, Oct 08, 2023 at 11:21:10AM +0530, Balaji G wrote: >> > > On Sat, 7 Oct 2023 at 02:50, Jeffrey Walton wrote: >> > > > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: >> > > > > >> > > > > Hi, >> > > > > >> > > > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version >> 5.16.12. >> > > > > When i do a link up/down i don't see any Gratuitous ARP being >> sent. >> > > > > >> > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify >> > > > > # ip link set down dev eno5np0 >> > > > > # ip link set up dev eno5np0 >> > > > > >> > > > > Captured all the packets via tcpdump & the tcpdump is not showing >> any >> > > > > Gratuitous ARP packets. >> > > > > >> > > > > But, with the same commands i could see the Gratuitous ARP being >> sent in >> > > > > Red hat.9.0 (Plow). >> > > > > >> > > > > So, please let me know if this is a specific scenario in Debian >> 11 ?? >> > > > >> > > > I think that's now Poettering: >> > > > >> > > > >> https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 >> > > > >> > > >> > > Do you mean this is a known issue & will be fixed in the future >> releases ? >> > >> > Here not Jeff. What I do understand from Jeff message is >> > something like: "I can bitch on systemd, so I do" >> > Time will tell how much Jeff contributes in solving >> > the interesting problem of the invisible gratuitous ARP. >> >> Nope, not that. >> >> I learned a long time ago to answer the question that was asked in the >> body of the post. >> >> You're welcome to complain about Systemd all you like. You won't get >> any complaints from me. It's not a discussion I will engage in. >> >> Jeff >> >
Re: Does the debian kernel sends the gratuitous arp ?
On Mon, Oct 09, 2023 at 08:39:02PM +0530, Balaji G wrote: > Hi Geert, Hello mailinglist (archive )readers of debian-user@lists.debian.org > >>> During `ip link set down dev eno5np0` and `ip link set up dev eno5np0` > >>> are NO IP-addresses involved. > > This interface eno5np0 is configured with the ip addresses(10.45.10.4 ). > > # ifconfig }( mismatch between `ifconfig` command expected `ifconfig` output ) > eno5np0: flags=4163 mtu 1500 > inet 10.45.10.4 netmask 255.255.255.0 broadcast 10.45.10.255 > ether 88:e9:a4:49:18:48 txqueuelen 1000 (Ethernet) > RX packets 2967346895 bytes 4417546189260 (4.0 TiB) > RX errors 0 dropped 1 overruns 0 frame 0 > TX packets 1634521866 bytes 2220475762246 (2.0 TiB) > TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 I did missed "LOWER_UP", then I noticed that `ifconfig` is used. More on that later. Back to 'Subject: Re: Does the debian kernel sends the gratuitous arp ?' To me is the answer "Yes, Debian kernel sends gratuitous ARP when it supposed to do". But we, this mailinglist, have this discussion because somewhere is the gratuitous ARP missing. What triggered the "I wonder why there is no gratuitous ARP?" is yet unknown. Let me try to capture a gratuitous ARP. I will be using only one interface (it is OK if the computer has many other network interfaces) Using two logins as root, one for "tcpdump", the other "set address". In "tcpdump session" tcpdump -n -i eth0 arp In "set address session" sudo ip address add 198.51.100.23/24 dev eth0 Back to "tcpdump session". And to my surprise: **no** gratuitous ARP ! It should be there. I even tried after: $ cat /proc/sys/net/ipv4/conf/eth0/arp_notify 0 $ echo 1 | sudo tee -a /proc/sys/net/ipv4/conf/eth0/arp_notify 1 $ cat /proc/sys/net/ipv4/conf/eth0/arp_notify 1 $ I'm gonna sleep about. Expect me back over 48 hours. > Thanks, Yeah, thanks for the good question. > Balaji Groeten Geert Stappers About ifconfig : https://serverfault.com/questions/633087/where-is-the-statement-of-deprecation-of-ifconfig-on-linux -- Silence is hard to parse
Re: Does the debian kernel sends the gratuitous arp ?
Hi Geert, >>> During `ip link set down dev eno5np0` and `ip link set up dev eno5np0` > are NO IP-addresses involved. This interface eno5np0 is configured with the ip addresses(10.45.10.4 ). # ifconfig eno5np0: flags=4163 mtu 1500 inet 10.45.10.4 netmask 255.255.255.0 broadcast 10.45.10.255 ether 88:e9:a4:49:18:48 txqueuelen 1000 (Ethernet) RX packets 2967346895 bytes 4417546189260 (4.0 TiB) RX errors 0 dropped 1 overruns 0 frame 0 TX packets 1634521866 bytes 2220475762246 (2.0 TiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 Thanks, Balaji On Sun, 8 Oct 2023 at 20:58, Jeffrey Walton wrote: > On Sun, Oct 8, 2023 at 4:58 AM Geert Stappers wrote: > > > > On Sun, Oct 08, 2023 at 11:21:10AM +0530, Balaji G wrote: > > > On Sat, 7 Oct 2023 at 02:50, Jeffrey Walton wrote: > > > > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > > > > > > > > > Hi, > > > > > > > > > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version > 5.16.12. > > > > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > > > > > > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > > > > # ip link set down dev eno5np0 > > > > > # ip link set up dev eno5np0 > > > > > > > > > > Captured all the packets via tcpdump & the tcpdump is not showing > any > > > > > Gratuitous ARP packets. > > > > > > > > > > But, with the same commands i could see the Gratuitous ARP being > sent in > > > > > Red hat.9.0 (Plow). > > > > > > > > > > So, please let me know if this is a specific scenario in Debian 11 > ?? > > > > > > > > I think that's now Poettering: > > > > > > > > > https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 > > > > > > > > > > Do you mean this is a known issue & will be fixed in the future > releases ? > > > > Here not Jeff. What I do understand from Jeff message is > > something like: "I can bitch on systemd, so I do" > > Time will tell how much Jeff contributes in solving > > the interesting problem of the invisible gratuitous ARP. > > Nope, not that. > > I learned a long time ago to answer the question that was asked in the > body of the post. > > You're welcome to complain about Systemd all you like. You won't get > any complaints from me. It's not a discussion I will engage in. > > Jeff >
Re: Does the debian kernel sends the gratuitous arp ?
Geert Stappers wrote: > On Fri, Oct 06, 2023 at 09:19:32PM +0200, Geert Stappers wrote: > > On Fri, Oct 06, 2023 at 05:52:16PM +0530, Balaji G wrote: > > > Hi, > > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel > > > version 5.16.12. When i do a link up/down i don't see any > > > Gratuitous ARP being sent. > > > > ARP > > Address Resolution Protocol > > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > > > Probably transmitted "I tried to enforce ARP notification" > > > > > > > # ip link set down dev eno5np0 > > > # ip link set up dev eno5np0 > > > > link > > As in "the link layer" > > > > > Captured all the packets via tcpdump & the tcpdump is not showing > > > any Gratuitous ARP packets. > > > > Why should it? (Yes, that is a serious question.) > > As opening question for further discussion. > > Because I like the question > Does the Debian kernel sends the gratuitous ARP ? > > I think the answer is YES > and I very curious when gratuitous ARP is ommitted. > > > > > But, with the same commands i could see the Gratuitous ARP being > > > sent in Red hat.9.0 (Plow). > > > > I think more factors have been change as kernel. > > As invitation for telling how the comparsion was done. > > > > > So, please let me know if this is a specific scenario in Debian > > > 11 ?? > > > > I state that the OP, Original Poster, is the specific scenario. > > Yeah, that is a blunt statement. Now hear me out. > > > > Gratuitous ARP is "linking" MAC-address and IP-address. > > > > During `ip link set down dev eno5np0` and `ip link set up dev > > eno5np0` are NO IP-addresses involved. > > > > So there is no need for ARP. > > > > > > I do hope to see a follow-up message like: > > > >Re-did the test with a static IP-address on the interface > >and indeed see a gratuitous ARP > > > > or some thing like > > > >To reproduce the missing gratuitous ARP do ... > > > > Yeah, that might reveal more information about dev eno5np0. > > > > > > > Thanks, > > > Balaji > > > > Groeten > > Geert Stappers > > Because in https://lists.debian.org/debian-user/2023/10/msg00212.html > I wrote "Lets follow-up > https://lists.debian.org/debian-user/2023/10/msg00181.html " If you'll forgive me stepping in ... I suspect neither Geert's nor Balaji's first language is English, and independently notice that Geert writes in a somewhat terse style whilst Balaji omits potentially useful information (such as the actual tcpdump output). So I'll add my summary of what I understand: Gert is pointing out that ARP packets are sent in connection with resolving the IP address associated with a MAC address, and that nothing that Balaji has posted suggests that an IP address has been allocated yet, so there would be no reason for a Gratuitous ARP packet to be sent. So he is interested to learn how the IP address is set up on both the Debian system and the Red Hat system (static or DHCP or something else?) and I suspect would ideally like to see sufficient message logs to demonstrate the truth of the answers. Specifically, on the Debian system is the IP address set statically, and are there any packets containing the IP address in the logs? Either transmitted or received. Similarly for the Red Hat system but perhaps less important. > Groeten > Geert Stappers
Re: Does the debian kernel sends the gratuitous arp ?
On Sun, Oct 8, 2023 at 4:58 AM Geert Stappers wrote: > > On Sun, Oct 08, 2023 at 11:21:10AM +0530, Balaji G wrote: > > On Sat, 7 Oct 2023 at 02:50, Jeffrey Walton wrote: > > > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > > > > > > > Hi, > > > > > > > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. > > > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > > > > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > > > # ip link set down dev eno5np0 > > > > # ip link set up dev eno5np0 > > > > > > > > Captured all the packets via tcpdump & the tcpdump is not showing any > > > > Gratuitous ARP packets. > > > > > > > > But, with the same commands i could see the Gratuitous ARP being sent in > > > > Red hat.9.0 (Plow). > > > > > > > > So, please let me know if this is a specific scenario in Debian 11 ?? > > > > > > I think that's now Poettering: > > > > > > https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 > > > > > > > Do you mean this is a known issue & will be fixed in the future releases ? > > Here not Jeff. What I do understand from Jeff message is > something like: "I can bitch on systemd, so I do" > Time will tell how much Jeff contributes in solving > the interesting problem of the invisible gratuitous ARP. Nope, not that. I learned a long time ago to answer the question that was asked in the body of the post. You're welcome to complain about Systemd all you like. You won't get any complaints from me. It's not a discussion I will engage in. Jeff
Re: Does the debian kernel sends the gratuitous arp ?
On Fri, Oct 06, 2023 at 09:19:32PM +0200, Geert Stappers wrote: > On Fri, Oct 06, 2023 at 05:52:16PM +0530, Balaji G wrote: > > Hi, > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > ARP Address Resolution Protocol > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > Probably transmitted "I tried to enforce ARP notification" > > > > # ip link set down dev eno5np0 > > # ip link set up dev eno5np0 > > link As in "the link layer" > > Captured all the packets via tcpdump & the tcpdump is not showing any > > Gratuitous ARP packets. > > Why should it? (Yes, that is a serious question.) As opening question for further discussion. Because I like the question Does the Debian kernel sends the gratuitous ARP ? I think the answer is YES and I very curious when gratuitous ARP is ommitted. > > But, with the same commands i could see the Gratuitous ARP being sent in > > Red hat.9.0 (Plow). > > I think more factors have been change as kernel. As invitation for telling how the comparsion was done. > > So, please let me know if this is a specific scenario in Debian 11 ?? > > I state that the OP, Original Poster, is the specific scenario. > Yeah, that is a blunt statement. Now hear me out. > > Gratuitous ARP is "linking" MAC-address and IP-address. > > During `ip link set down dev eno5np0` and `ip link set up dev eno5np0` > are NO IP-addresses involved. > > So there is no need for ARP. > > > I do hope to see a follow-up message like: > >Re-did the test with a static IP-address on the interface >and indeed see a gratuitous ARP > > or some thing like > >To reproduce the missing gratuitous ARP do ... > > Yeah, that might reveal more information about dev eno5np0. > > > > Thanks, > > Balaji > > Groeten > Geert Stappers Because in https://lists.debian.org/debian-user/2023/10/msg00212.html I wrote "Lets follow-up https://lists.debian.org/debian-user/2023/10/msg00181.html " Groeten Geert Stappers -- Silence is hard to parse
Re: Does the debian kernel sends the gratuitous arp ?
On Sun, Oct 08, 2023 at 11:21:10AM +0530, Balaji G wrote: > On Sat, 7 Oct 2023 at 02:50, Jeffrey Walton wrote: > > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > > > > > Hi, > > > > > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. > > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > > # ip link set down dev eno5np0 > > > # ip link set up dev eno5np0 > > > > > > Captured all the packets via tcpdump & the tcpdump is not showing any > > > Gratuitous ARP packets. > > > > > > But, with the same commands i could see the Gratuitous ARP being sent in > > > Red hat.9.0 (Plow). > > > > > > So, please let me know if this is a specific scenario in Debian 11 ?? > > > > I think that's now Poettering: > > > > https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 > > > > Jeff > > > Hi Jeff, > > Do you mean this is a known issue & will be fixed in the future releases ? > Here not Jeff. What I do understand from Jeff message is something like: "I can bitch on systemd, so I do" Time will tell how much Jeff contributes in solving the interesting problem of the invisible gratuitous ARP. Meanwhile lets follow-up on https://lists.debian.org/debian-user/2023/10/msg00181.html > Thanks, > Balaji You might have an extra copy of this message. Because I did this time "reply-to-all" insteadof "reply-to-list". The good thing of "reply-to-list" is that it reveals who reads mailinglist postings. Yes, I'm trying to tell that you missed https://lists.debian.org/debian-user/2023/10/msg00181.html Regards Geert Stappers -- Silence is hard to parse
Re: Does the debian kernel sends the gratuitous arp ?
Hi Jeff, Do you mean this is a known issue & will be fixed in the future releases ? Thanks, Balaji On Sat, 7 Oct 2023 at 02:50, Jeffrey Walton wrote: > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > > > Hi, > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version > 5.16.12. > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > # ip link set down dev eno5np0 > > # ip link set up dev eno5np0 > > > > Captured all the packets via tcpdump & the tcpdump is not showing any > Gratuitous ARP packets. > > > > But, with the same commands i could see the Gratuitous ARP being sent in > Red hat.9.0 (Plow). > > So, please let me know if this is a specific scenario in Debian 11 ?? > > I think that's now Poettering: > > https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 > > Jeff >
Re: Does the debian kernel sends the gratuitous arp ?
On Sat, Oct 7, 2023 at 1:38 AM wrote: > > On Fri, Oct 06, 2023 at 05:20:22PM -0400, Jeffrey Walton wrote: > > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > > > > > Hi, > > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version > > > 5.16.12. > > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > > # ip link set down dev eno5np0 > > > # ip link set up dev eno5np0 > > > > > > Captured all the packets via tcpdump & the tcpdump is not showing any > > > Gratuitous ARP packets. > > > > > > But, with the same commands i could see the Gratuitous ARP being sent in > > > Red hat.9.0 (Plow). > > > So, please let me know if this is a specific scenario in Debian 11 ?? > > > > I think that's now Poettering: > > https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 > > As Geert says, probably it needs an ip address to be able to send > an ARP. Perhaps the Redhat box has one set by default? OP asked if this was specific to Red Hat. The answer is No, it is baked into Systemd nowadays. > What does "ip addr show dev " say? I have no idea. Jeff
Re: Does the debian kernel sends the gratuitous arp ?
On Fri, Oct 06, 2023 at 05:20:22PM -0400, Jeffrey Walton wrote: > On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > > > Hi, > > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. > > When i do a link up/down i don't see any Gratuitous ARP being sent. > > > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > > # ip link set down dev eno5np0 > > # ip link set up dev eno5np0 > > > > Captured all the packets via tcpdump & the tcpdump is not showing any > > Gratuitous ARP packets. > > > > But, with the same commands i could see the Gratuitous ARP being sent in > > Red hat.9.0 (Plow). > > So, please let me know if this is a specific scenario in Debian 11 ?? > > I think that's now Poettering: > https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 As Geert says, probably it needs an ip address to be able to send an ARP. Perhaps the Redhat box has one set by default? What does "ip addr show dev " say? Cheers -- t signature.asc Description: PGP signature
Re: Does the debian kernel sends the gratuitous arp ?
On Fri, Oct 6, 2023 at 2:04 PM Balaji G wrote: > > Hi, > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. > When i do a link up/down i don't see any Gratuitous ARP being sent. > > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify > # ip link set down dev eno5np0 > # ip link set up dev eno5np0 > > Captured all the packets via tcpdump & the tcpdump is not showing any > Gratuitous ARP packets. > > But, with the same commands i could see the Gratuitous ARP being sent in Red > hat.9.0 (Plow). > So, please let me know if this is a specific scenario in Debian 11 ?? I think that's now Poettering: https://github.com/systemd/systemd/blob/main/src/libsystemd-network/sd-ipv4acd.c#L302 Jeff
Re: Does the debian kernel sends the gratuitous arp ?
On Fri, Oct 06, 2023 at 05:52:16PM +0530, Balaji G wrote: > Hi, > I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. > When i do a link up/down i don't see any Gratuitous ARP being sent. ARP > # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify Probably transmitted "I tried to enforce ARP notification" > # ip link set down dev eno5np0 > # ip link set up dev eno5np0 link > Captured all the packets via tcpdump & the tcpdump is not showing any > Gratuitous ARP packets. Why should it? (Yes, that is a serious question.) > But, with the same commands i could see the Gratuitous ARP being sent in > Red hat.9.0 (Plow). I think more factors have been change as kernel. > So, please let me know if this is a specific scenario in Debian 11 ?? I state that the OP, Original Poster, is the specific scenario. Yeah, that is a blunt statement. Now hear me out. Gratuitous ARP is "linking" MAC-address and IP-address. During `ip link set down dev eno5np0` and `ip link set up dev eno5np0` are NO IP-addresses involved. So there is no need for ARP. I do hope to see a follow-up message like: Re-did the test with a static IP-address on the interface and indeed see a gratuitous ARP or some thing like To reproduce the missing gratuitous ARP do ... Yeah, that might reveal more information about dev eno5np0. > Thanks, > Balaji Groeten Geert Stappers -- Silence is hard to parse
Does the debian kernel sends the gratuitous arp ?
Hi, I am using "Debian GNU/Linux 11 (bullseye)" with kernel version 5.16.12. When i do a link up/down i don't see any Gratuitous ARP being sent. # echo 1 > /proc/sys/net/ipv4/conf/eno5np0/arp_notify # ip link set down dev eno5np0 # ip link set up dev eno5np0 Captured all the packets via tcpdump & the tcpdump is not showing any Gratuitous ARP packets. But, with the same commands i could see the Gratuitous ARP being sent in Red hat.9.0 (Plow). So, please let me know if this is a specific scenario in Debian 11 ?? Thanks, Balaji
