From nobody Mon Jul 18 08:35:33 2022 X-Original-To: freebsd-questions@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4LmZzm5zjjz4WkMb for ; Mon, 18 Jul 2022 08:35:48 +0000 (UTC) (envelope-from gray@nxg.name) Received: from mx1.mythic-beasts.com (mx1.mythic-beasts.com [IPv6:2a00:1098:0:86:1000:0:2:1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4LmZzm1JCwz4M6r; Mon, 18 Jul 2022 08:35:48 +0000 (UTC) (envelope-from gray@nxg.name) Received: from [2001:8b0:df5:af53:145f:9bba:ee3:486c] (port=51282 helo=[192.168.0.14]) by mailhub-cam-d.mythic-beasts.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1oDMEE-007rIu-0R; Mon, 18 Jul 2022 09:35:46 +0100 From: Norman Gray To: Kevin Oberman Cc: FreeBSD Questions , Kristof Provost Subject: Re: Why can't I add a loopback interface to a bridge? Date: Mon, 18 Jul 2022 09:35:33 +0100 X-Mailer: MailMate (1.14r5769) Message-ID: <00939711-A51C-4ADA-B68F-9D12B2F9645B@nxg.name> In-Reply-To: References: <988896FB-9986-4955-A3B7-9CEC810D8E6E@nxg.name> List-Id: User questions List-Archive: https://lists.freebsd.org/archives/freebsd-questions List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-BlackCat-Spam-Score: 9 X-Spam-Status: No, score=0.9 X-Rspamd-Queue-Id: 4LmZzm1JCwz4M6r X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of gray@nxg.name designates 2a00:1098:0:86:1000:0:2:1 as permitted sender) smtp.mailfrom=gray@nxg.name X-Spamd-Result: default: False [-2.50 / 15.00]; SUBJECT_ENDS_QUESTION(1.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; NEURAL_HAM_SHORT(-1.00)[-1.000]; NEURAL_HAM_LONG(-1.00)[-0.999]; RCVD_IN_DNSWL_MED(-0.20)[2a00:1098:0:86:1000:0:2:1:from]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1098::86:1000:0:2:0/112]; MIME_GOOD(-0.10)[text/plain]; R_DKIM_NA(0.00)[]; MLMMJ_DEST(0.00)[freebsd-questions@freebsd.org]; FREEMAIL_TO(0.00)[gmail.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:44684, ipnet:2a00:1098::/32, country:GB]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_ALL(0.00)[]; TO_MATCH_ENVRCPT_SOME(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; ARC_NA(0.00)[]; RCVD_TLS_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; DMARC_NA(0.00)[nxg.name]; RCPT_COUNT_THREE(0.00)[3]; RCVD_COUNT_TWO(0.00)[2] X-ThisMailContainsUnwantedMimeParts: N Kevin, hello. On 14 Jul 2022, at 18:31, Kevin Oberman wrote: > What may be missing is the concept of a bridge is that it is a layer 2 > connection between two or more 802-like devices. Such devices use MAC > addresses and an IP address is a layer 3 entity. Trying to mix such on > a > bridge would imply a routing capability (layer 3) which really does > not > make sense with a layer 2 device. Indeed -- the presence of both layer 2 and layer 3 elements in the if_bridge(4) description at least contributed to my confusion. In my simple-minded picture of 'a switch', the only layer 3 element is a possible management interface. However Kristof's remark that > An if_bridge is not just a switch, but also a NIC that’s plugged > into that switch. is a valuable one, to the extent that I think it would be worthwhile somehow incorporating it into the manpage, in the paragraph starting 'A bridge works like a switch,...' I do see that amongst the examples at the end of the manpage there there is a remark 'The bridge can be used as a regular host interface at the same time as bridging between its member ports', so there is an implication of 'a NIC that's plugged into the switch'. Best wishes, Norman -- Norman Gray : https://nxg.me.uk