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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id t3-20020a170902e84300b001e3d8c237a2sm8788617plg.260.2024.04.10.08.21.59 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Apr 2024 08:21:59 -0700 (PDT) Date: Wed, 10 Apr 2024 08:21:53 -0700 From: Stephen Hemminger To: netdev@vger.kernel.org Subject: Fw: [Bug 218700] New: the arp table may contain a fake IP address Message-ID: <20240410082153.7d12bba1@hermes.local> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit This looks like a side effect of the Linux neighbor table and weak host model. So don't get too worried about it. Begin forwarded message: Date: Wed, 10 Apr 2024 07:08:57 +0000 From: bugzilla-daemon@kernel.org To: stephen@networkplumber.org Subject: [Bug 218700] New: the arp table may contain a fake IP address https://bugzilla.kernel.org/show_bug.cgi?id=218700 Bug ID: 218700 Summary: the arp table may contain a fake IP address Product: Networking Version: 2.5 Hardware: All OS: Linux Status: NEW Severity: normal Priority: P3 Component: IPV4 Assignee: stephen@networkplumber.org Reporter: a_s_y@sama.ru Regression: No An entry from an incorrect interface may get into the arp table: # arp -n|grep 100.64.1.113 100.64.1.113 ether 50:ff:20:26:fa:14 C ether9.3109 100.64.1.113 (incomplete) ether1.2115 # ip -4 a s dev ether9.3109 1829: ether9.3109@ether9: mtu 1500 qdisc noqueue state UP group default qlen 1000 inet 100.64.3.62/30 brd 100.64.3.63 scope global ether9.3109 valid_lft forever preferred_lft forever # ip -4 a s dev ether1.2115 1822: ether1.2115@ether1: mtu 1500 qdisc noqueue state UP group default qlen 1000 inet 100.64.1.114/30 brd 100.64.1.115 scope global ether1.2115 valid_lft forever preferred_lft forever ether9.3109 and ether1.2115 are 802.1q VLAN, I don't know if it's important. The ether9.3109 interface receives traffic from forgotten hardware (tcpdump -e -ni ether9 host 100.64.1.113): 10:57:08.861954 50:ff:20:26:fa:14 > Broadcast, ethertype 802.1Q (0x8100), length 64: vlan 3109, p 0, ethertype ARP, Request who-has 100.64.1.114 tell 100.64.1.113, length 46 kernel reply is 1) exists, although the ether9.3109 interface does not contain 100.64.1.114 2) contain the MAC of ether9.3109: 10:57:08.861972 3c:ec:ef:4d:94:ee > 50:ff:20:26:fa:14, ethertype 802.1Q (0x8100), length 46: vlan 3109, p 0, ethertype ARP, Reply 100.64.1.114 is-at 3c:ec:ef:4d:94:ee, length 28 # ip a| grep 100.64.1.114 inet 100.64.1.114/30 brd 100.64.1.115 scope global ether1.2115 -- You may reply to this email to add a comment. You are receiving this mail because: You are the assignee for the bug.